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    Analysis of Design Factors for Power, Heating, Ventilating, and Refrigeration Systems

    Encyclopedia Arctica 2b: Electrical and Mechanical Engineering

    Unpaginated      |      Vol_IIB-0119                                                                                                                  
    EA-I. (William Everett Potter)





    I. Steam Power and Heating Plants 1
    Climate 1
    Permafrost 3
    Ice Fog 4
    Snow 5
    Earthquakes 5
    Location 5
    Fuels 6
    Coal Handling 7
    Condensing Water Facilities 8
    Intake Air Heaters 9
    Space Heating 10
    Temporary Plants 11
    Interchangeability 12
    II. Steam Distribution Systems 12
    General Design Factors 13
    Types of Installations 14
    Temporary Utilidors 17
    Central Steam Distribution vs. Individual Space Heating 18
    Radiant Heating 18
    III. Ventilating and Refrigeration Systems 19
    Ventilating Systems 19
    Refrigeration Systems 22

    Unpaginated      |      Vol_IIB-0120                                                                                                                  
    EA-I. Potter: Analysis of Design Factors



            With the manuscript of this article, the author submitted 8

    photographs for possible use as illustrations. Because of the high

    cost of reproducing them as halftones in the printed volume, only a

    small proportion of the photographs submitted by contributors to

    Volume I, Encyclopedia Arctica , can be used, at most one o r two with

    each paper; in some cases none. The number and selection must be

    determined later by the publisher and editors of Encyclopedia Arctica .

    Meantime all photographs are being held at The Stefansson Library.

    001      |      Vol_IIB-0121                                                                                                                  
    EA-I. (William Everett Potter)






            The design of steam power and steam-heating plants for use in the

    Arctic and Subarctic will differ from that for similar plants in the United States

    only insofar as the designs are influenced by factors peculiar to the climate,

    geology, and location of the region in which the plant is to be constructed.

    Following is a review of these general conditions and of the factors to be

    considered in designs for Alaskan plants.

            Climate . Alaska with its lofty mountains, glaciers, snow fields and

    broad alluvial plains, presents a great variety of climate, controlled

    largely by the mountain ranges and the modifying effect of the Japan current.

            Climatologically, Alaska is a land of extremes; temperatures of 100° F.

    in the summer and −78° F. in winter have been recorded at Fort Yukon. Pre–

    capitation varies widely also; an average annual maximum of 155.52 inches

    (7-year record) was recorded at View Cove in the south coastal area, while

    Barrow in the northern region has an average annual minimum of 4.34 inches

    (23-year record). However, as a whole and particularly north of the Alaska

    Range, it is a relatively arid country as is the case in most arctic and

    subarctic regions.

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    EA-I. Potter: Power, Heating, Ventilating, and Refrigeration Systems

    From the standpoint of engineering design, Alaska may well be divided

    into four climatic areas, although it should be understood that conditions

    within these areas vary widely in some respects.

            From Cook Inlet southerly along the coast, the climate is comparable

    to that of north coastal New England except for annual precipitation which

    averages 150 inches in some localities. Here, temperatures range to 75° F.

    in the summer and rarely drop below 0° F. in the winter. High winds are

    prevalent throughout the year.

            In the area north of Cook Inlet and south of the Alaska Range, the

    climate is comparable to that of north-central United States. Average annual

    precipitation is approximately 14.5 inches, snow is light and powdery,

    averaging about 4 feet. Temperatures run from a maximum of 90° F. to a mini–

    mum of −40° F. for regions with established records. Areas within this

    general region probably exist in which minimum temperatures range lower than

    −40° F. Low wind velocities are the rule, although gust velocities of 60 to

    70 miles per hour are sometimes attained and velocities in excess of 100 miles

    per hour have been recorded.

            The long Aleutian chain has a climate somewhat different from the coastal

    region. In this area a considerable range of wind velocity prevails, with

    less differential prevailing for the temperature and precipitation aspects.

    The general situation can be described as follows: The general average annual

    precipitation does not exceed 50 inches, with far more rain than s h n ow as the

    rule. Temperatures range from 67° F. average maximum to 35° F. average mini–

    mum. Wind velocities are high and range to 100 miles per hour or better for

    extreme gusts, with a general maximum range of about 60 to 69 miles per hour.

            In the region north of the Alaska Range and south of the polar areas,

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    EA-I. Potter: Power, Heating, Ventilating, and Refrigeration Systems

    precipitation will vary from an annual average of 13.63 inches (38-year

    period) at Tanana to the extremely low annual average of 4.34 inches at

    Barrow. Temperatures range from the extremes of 100° F. to −78° F. The

    low temperatures generally occur in the interior. Winds are usually light.

            The various physical phenomena resulting from these climatic conditions

    and from which much of the design criteria are evolved are reviewed herewith.

            Permafrost . The term “permafrost” refers to the permanently frozen

    soils occurring at various depths below the earth’s surface in those rela–

    tively arid regions where mean annual temperatures are below freezing. It

    may take the form of a continuously frozen layer several hundred feet in depth,

    in alternate and relatively shallow layers of frozen and unfrozen materials

    or in islands. The surface layer in a permafrost area is, of course, subject

    to alternate freezing and thawing with the seasons, and is the so-called active

    layer. The layer separating the active zone from the permanently frozen mate–

    rial is defined as the permafrost table. Ground temperatures in permafrost

    vary but little the year round, ranging from 26° to 30° F. near the surface,

    and stabilizing, in the Fairbanks area, at a depth of about 100 feet. As

    approximately 80% of Alaska is in the permafrost belt, it is a factor which

    should be thoroughly investigated prior to the development of final designs.

            The extent to which this condition will affect designs is dependent on

    the type of the formation, the depth at which it occurs below the ground

    surface, the height of the ground-water table and the nature of the soils.

    At locations where p a e rmafrost is composed of well-graded granular particles

    which are stable when either thawed or frozen, its presence will have little

    effect on foundation designs. Where conditions of instability are met in

    the form of high ground water table and fine-grained soils, suitable design

    criteria must be adopted to eliminate the possibility of future settlement.

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    If the stratum of fine-grained soils is shallow, it may be removed entirely

    and replaced with a mat of coarse, but well-graded and thoroughly compacted

    sand and gravel.

            In all investigations of this nature, it should be remembered that

    disturbing the ground surface by removing or altering the depth of its

    vegetal covering or excavating for foundations may change the relative posi–

    tion of the permafrost table quite appreciably, and the possibility and probable

    extent of such an occurrence should also be studied carefully.

            In conclusion, with respect to permafrost and its relation to power plants,

    the principal point to consider is the need for a thorough subsurface investi–

    gation of the site or several sites if conditions warrant and, after careful

    study and analysis of all factors, to develop a set of design criteria appli–

    cable to the particular conditions encountered. The importance of such

    studies leading to the development of adequate design criteria can be readily

    appreciated when considered in the light of the disastrous consequences bound

    to follow structural failure.

            Ice fog is a condition prevalent in cold regions and generally occurs in

    relatively low areas. It is formed by extremely cold air “flowing” down from

    the mountains into the valleys, displacing the warmer air, and condensing out

    moisture in the form of tiny ice particles that remain in suspension. It is

    a natural phenomenon that will occur and be dispelled by changes in atmospheric

    conditions and can be sufficiently heavy to close down air operations completely.

            The most carefully designed power plants will give off gases and dust to

    some degree, thus aggravating f t he ice-fog condition and it is, therefore,

    essential that some thought be given the matter, with particular regard to

    location. In this respect, the ideal arrangement would be to locate the air

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    EA-I. Potter: Power, Heating, Ventilating, and Refrigeration Systems

    strip on the highest elevation, residential areas at a slightly lower eleva–

    tion, and the industrial area and power plant at a still lower elevation.

    This, as mentioned, is an ideal layout, but physical conditions are rarely

    such as to permit its accomplishment. Accordingly, where the steam power

    plant and its cooling water facilities must be set at the same elevation as

    the air strip, they should be located to leeward if at all possible. The

    plant should be provided with automatic combustion control and fly-ash

    precipitators. Exhausting steam and vapors to the atmosphere should be

    eliminated insofar as it is economically possible.

            Snow . The heavy snowfalls prevalent in the south-central area of Alaska

    not only require heavier structural designs, but must be recognized as a con–

    dition contributory to halting or delaying transportation and, as a consequence,

    emphasizing the need for adequate fuel reserves.

            Earthquakes . Many sections of Alaska are subject to periodic earthquake

    shock. (See also “Earthquakes in the Arctic Area.”) The areas in the vicinity

    of Anchorage and Fairbanks have experienced frequent quakes. The disastrous

    consequences of earthquake damage are readily appreciated; therefore, all

    structures must be designed to reduce to a minimum the possibility of damage

    occurring through this medium. Design criteria in this connection have been

    established by the Pacific Coast Building Officials conference and is pub–

    lished in their Uniform Building Code, 1946 Edition.

            Location . Alaska comprises the northwestern extremity of North America

    west of the 141st meridian, a strip of coastal land extending south to 55° N.

    latitude, and all adjacent islands. Its most northerly limit extends to

    Point Barrow, about 300 miles north of the Arctic Circle. Total land and

    water area is approximately 591,000 square miles. By and large, Alaska is a

    particularly isolated country. Shipping, except for a few ports along the

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    EA-I. Potter: Power, Heating, Ventilating, and Refrigeration Systems

    south coast, is restricted to the summer months. Rail facilities are

    limited and, with all due respect, hardly on a par with operating lines

    in the United States. Natural resources are relatively undeveloped, local

    manufacturing negligible, and skilled labor is available in relatively

    limited numbers only. These several factors impose an economic condition

    equally unfavorable to all types of construction. Aside from this more or

    less universal condition, location affects power-plant designs largely

    through the factor of transportation. Rail service is frequently disrupted

    and delayed by excessive snowfall, earthquakes, landslides, and flood, and,

    as a consequence, abnormally large fuel storage facilities must be provided.

            Fuels. It is axiomatic that coal of the highest quality obtainable at

    a relatively reasonable price results in a more economical and efficiently

    operating plant. Losses sustained in burning low-grade coal are not limited

    to the loss in heating value alone. More fuel must be transported and

    handled and larger grates are needed to burn it in order to obtain the heat

    required by the boiler. Greater quantities of ash must be handled and the

    percentage of unburned coal in the ash will run higher. The greatest loss

    in the use of low-grade fuel comes about through the inefficient heat absorp–

    tion in the boiler as a result of the lower furnace temperatures obtainable.

    This is very important since a large part of the heat available to the boilers

    is radiant heat obtained directly from the furnace, and the higher the furnace

    temperature the better the heat absorption. The high furnace temperatures

    conducive to efficient operation cannot be obtained from low-grade coal.

    Coal is mined in Alaska and, although of low grade (for purposes of design

    it is assumed to have a heating value of 9,000 B.t.u. per pound), it is

    probably the most economical fuel to use. Oil is not produced in Alaska and

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    EA-I. Potter: Power, Heating, Ventilating, and Refrigeration Systems

    would have to be imported if used. Too, the heavier and cheaper grades of

    oils ordinarily used for fuels are extremely viscious and do not flow readily

    at Atlaskan winter temperatures. This necessitates insulating and equipping

    pipelines with steam tracers, increasing the cost appreciably. On the other

    hand, the less visc i ous fuel oils, although more expensive, can be handled

    by pipeline without undue difficulty and at far less cost than that afforded

    by rail facilities. If and when the synthetic production of liquid fuels

    from coal becomes a commercially economical enterprise, it should be thoroughly

    investigated for exploitation and development in Alaska. However, until that

    time comes, the locally mined coal will in all probability prove to be the more

    economical and dependable fuel.

            Coal Handling . Aside from outside reserve storage, this phase of the

    design involves several units. Coal on route from the mines during the cold

    weather invariably arrives at its destination frozen solidly in the car and,

    as a consequence, thawing facilities must be included in the plant design

    (Fig. 1). This involves furnishing a structure enclosing a spur track of

    sufficient size to accommodate one to several cars. Heat for thawing may be

    provided by a system of steam coils arranged on the wall along either side of

    and parallel with the car or cars and unit heaters overhead, or by a series of

    open flame pits located under the track and between the rails at specified

    intervals which throw off an intense radiant heat, melting the ice and snow in

    a comparatively short time. It is, of course, obvious that an adequate drain–

    age system will be required in connection with either system.

            After thawing, the cars are dumped in a track hopped where the coal is

    carried by a suitable conveyer to the crushers and reduced to the proper size.

    After passing through the crusher it is carried by elevator conveyer to a

    head house where it can be disposed to any one of three points as required:

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    ( 1 ) by horizontal conveyer to the stoker feed hoppers, ( 2 ) by gravity and

    horizontal conveyer to covered and heated storage bins, ( 3 ) by gravity to an

    exterior truck-loading port for return to outside storage reserves. This last

    mentioned would be used only in the event heated storage bins and the stoker

    feed hoppers are full. Coal can be taken from the heated storage as and

    when required, by horizontal conveyer back to the elevator conveyer, up to

    the head house, and into the stoker feed hoppers (Fig. 2). The heated storage

    bins should be of ample size to permit storage sufficient to meet anticipated


            Outside reserve storage areas should be located as close to the plant as

    conditions will permit. Coal so stored will freeze solidly and, unless some

    mechanical means is adopted to aid in the thawing process, it must be blasted

    and broken to a fineness such that it will enter the crushing equipment.

    Probably the most satisfactory method to use in this instance is a grid of

    steam pipes buried under the stockpiles, installed in conveniently sized

    and individually controlled sections for the sake of economy.

            Condensing Water Facilities . An ample supply of condenser cooling water

    must be available. If the plant is located near a river or pond having an

    adequate year-round supply, a satisfactory system may be had by the installa–

    tion of suitably sized intake and discharge lines. Pipelines of this nature

    will not freeze even if laid in the ground and uninsulated, because the water

    gains some heat from the condenser and is in constant circulation.

            Water from a natural source is not always conveniently or economically

    available, in which even it may be practicable to construct an artificial

    pond in the immediate vicinity of the plant. Surface area is the controlling

    factor in an artificial cooling pond and depth is of small consequence.

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    EA-I. Potter: Power, Heating, Ventilating, and Refrigeration

    Cooling ponds of this type will require approximately 150,000 square feet

    of surface areas for every 1,000 kilo/ [ ?] watts of turbogenerator capacity. If

    the required area is not available, similar and equally satisfactory results

    may be had by reducing the pond area to that required for winter use and

    installing spray devices to gain the additional surface area required for

    summer use. The use of a spray pond during the winter is not desirable as

    it would tend to aggravate the conditions of ice fog prevalent in the cold


            The most compact method of cooling condenser water is provided by the

    Fig. 3 cooling tower (Fig. 3); however, experience has indicated this to be not

    entirely satisfactory in winter operations, because of icing difficulties.

    The fans blow a fine spray at the entrance which freezes and builds up ice to

    the extent that the fans are no longer operable; this reduces cooling capacity

    so much that the generator must operate at reduced load. Inasmuch as winter

    is normally the season of heaviest electrical loads, loss of potential

    generating capacity at this time becomes a serious problem. Obviously then,

    this method of cooling condenser water should be discarded.

            Intake Air Heaters . In consideration of the low temperatures likely to

    be encountered in Alaska, it is necessary to provide some means for heating

    intake air. In many localities within the United States, air heaters can

    frequently make use of stack gases and thus operate more economically. Where

    extremely low temperatures are the rule, it becomes necessary to adopt some

    other means of supplying the intake air heaters, as extreme care must be

    taken not to reduce stack gases below a temperatures at which condensation

    will occur in the heate e r or the stack, as the resulting erosion would quickly

    destroy these items of equipment. Danger from this source can be eliminated

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    by using steam heat o e rs. Insulation must be provided at that portion of the

    air intake exposed to the atmosphere as otherwise frost and ice will accu–

    mulate inside the duct work. Insulation must also be provided around the

    exposed surfaces of boiler stacks to prevent possible condensation and

    subsequent corrosion.

            The effect of extreme cold in such cases must be seen to be appreciated.

    A bolt passing through the side of a building results in a heat loss diffi–

    cult to realize. The head of the bolt will become coated with frost and

    ice to a considerable thickness even insi [ ?] d e a heated building. It is there–

    fore, essential that all pipes, ducts, and other metal devices that are

    exposed to extremes of temperature be adequately insulated.

            Space Heating . In the development of a steam plant to serve the dual

    purpose of providing central steam for space heating and as a source of power

    in the production of electrical energy, the most economical over-all design

    embraces the use of turbine exhaust steam for space heating. By so doing,

    power can be generated at low cost. In order to balance the steam required

    4 for heating purposes with that available from the turbogenerators (Fig. 4),

    extraction-type turbines are normally used. This type of equipment permits

    taking steam from the turbine at any desired pressure from zero to full

    extraction with the balance of the steam not required for heating purposes

    going into the condenser. From time to time it may happen that more steam

    is required for heating than is available from the extraction turbines, in

    which event it can be obtained by passing the high-pressure steam from the

    boilers through a reducing valve set to furnish additional steam at the

    pressure required by the heating system. This arrangement is quite simple

    and is generally used in the design of dual-purpose plants. When all of

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    the turbine exhaust steam is to be utilized for heating, the turbine exhaust

    is piped directly to the steam distribution system. This turbine is termed

    the “back pressure” type.

            Temporary Plants . Approximately three years are required to design

    and construct a steam power plant of the size ordinarily required by a per–

    manent military establishment in Alaska, although steam for heating can be

    had from the boilers in approximately half of this time. In the meantime

    both steam for heating and electrical power are required for use during the

    construction period and to service post facilities as they are completed.

    This, of course, necessitates the erection of plants of a temporary nature.

    As this procedure involves a considerable item of expense from which there

    is small return, design and construction schedules should be so planned as

    to hold the demand for plants of this type to a minimum. Many military units

    require stand-by service of this nature as a matter of military necessity. Advance planning should, therefore, consider this factor with a view to

    incorporating the temporary plant in part or in its entirety into the perma–

    nent over-all layout, possibly as a stand-by.

            Both power and heating plants are required for servicing mobilization–

    type construction which, while not of a strictly temporary nature, would

    hardly be classified as permanent-type units. In general, capacity require–

    ments for mobilization-type plants will be less than for permanent type, and

    many of the structural and mechanical refinements essential to the economical

    and efficient operation of a permanent plant can be eliminated entirely.

            Design of a plant for strictly temporary purposes should consider the

    use of packaged-type steam boilers and power-generating equipment, as these

    units can be placed in service in a very short time after delivery to the

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    site. Too, if the ultimate in mobility is desired, they can be set up on

    flat cars or motor trailers, where suitable rail or highway facilities are

    available, and moved about as needed with relative case.

            Over-all design should be of extreme simplicity, embodying only those

    features assuring structural soundness and a reasonable degree of mechanical

    efficiency consistent with the purpose for which the plant is to be used.

            Interchangeability . Consideration should be given to standardization

    of equipment and parts within a plant. It is an advantage to standardize

    plants and methods as much as possible for the interchange of equipment and

    personnel. Particularly is this true of military installations which may be

    destroyed or crippled and require the transfer of operators from one plant

    to another during an emergency, or for any other reason. It should be borne

    in mind that in such an isolated section, with transportation difficulties,

    expert servicing is not readily available. All of which points to the need

    for simple, rugged equipment. Also, plants should be so designed as to

    facilitate expansion to handle additional loads due to constantly changing

    military requirements and strategy.



            The mechanical features of steam distribution systems in Alaska are, in

    general, identical with those for such systems in the United States, except

    that provision must be made for extremes of climate, permafrost, and earthquake

    conditions which have been described in Section I. Too, over-all design will

    be dependent on whether it is to be a permanent or a temporary installation.

    Although this article frequently mentions the e d esign factors specifically in

    relation to military installations, these same factors are applicable to other

    industrial structures of similar size.

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            General Design Factors . Facilities within a military reservation are

    frequently laid out in widely dispersed units. To hold steam distribution

    pipe sizes to economical diameters where the pipes extend to distances up

    to 10,000 feet from the central station, distribution pressures of about

    200 p.s.i. should be maintained. Reducing stations must be provided in

    each area served, where the main line pressure is dropped to about 60 p.s.i.,

    this latter pressure being reduced still further within the various buildings

    to anywhere from 2 to 15 p.s.i. dependent on the needs of the particular

    building. Pipes are sized in accordance with the quantity of steam to be

    delivered and the pressure required at the end of the line. A 10% allowance

    for condensation is usually added to the demand quantity of steam.

            Pumped condensate returns are considered to be more satisfactory than a

    gravity system, as the former may be installed without regard to slope.

    Manholes should not, in general, be spaced in excess of 500 feet unless condi–

    tions are unusually favorable. Such a condition is encountered occasionally

    in the form of a long, straight run with downgrades in the direction of steam

    flow. Manholes will contain condensate pumps, control valves, expansion joints,

    traps, and other items of equipment necessary to the prop [ ?] e r operation of the

    system. Steam supply mains should be provided with double standard-thickness

    insulation. Return lines may or may not be insulated, depending on the parti–

    cular circumstances. This is usually governed by the economies involved and

    will generally mean that high-pressure-condensate returns will be insulated

    and the low-pressure returns will not be insulated. Duplex condensate pumps

    should be provided as a guarantee of continuous service. They should be auto–

    matically controlled for interchange and picking up the load one from the other,

    in the event one unit should fail, through motor or mechanical trouble.

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            Expansion joints must, of course, be installed at specified intervals,

    together with the necessary anchors. These may be either the compact,

    accordion-type joint, or a suitably sized loop. Selection between types

    is also a question of economy. In the larger sized mains, the accordion

    type is the more economical, whereas from eight inches down there is very

    little difference in cost. If the steam mains are carried in an underground

    pipe gallery along with sewer and water mains, the accordion-type joint will

    probably be the more economical regardless of pipe sizes.

            Types of Installations . Either one of two general methods may be adopted

    in the installation of steam distribution mains. The main can be buried in

    the ground, carried on posts just above the ground surface, carried on a pole

    line sufficiently high in the air to clear all ordinarily anticipated vehicu–

    lar traffic, or it can be installed in an underground pipe gallery or tunnel

    in company with water supply and sewage collection mains. (See also “Arctic

    Sanitary Engineering.”)

            If the steam main is buried in the ground (Fig. 5), it must be insulated

    and jacketed to assure watertightness. There are several patented mains of

    this type on the market. On some of these, the supply main and condensate

    returns are made up as a single insulated and metal-jacketed unit in the

    smaller sizes. In the larger sizes, the supply and condensate mains are

    made up as individual units. This type proves to be quite satisfactory where

    it can be installed in the trench above the ground-water table and in the

    absence of permafrost. However, if installed below the ground-water table,

    corrosion eventually causes the metal jacket to leak allowing moisture to

    work into the insulation, the moisture is vaporized by the heat from the main,

    and, in some cases, will build up a head of steam sufficient to rupture the

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    metal jacket and blow out the insulation. Even if this does not happen,

    the accumulation of moisture in the insulation destroys its effectiveness

    and results in excessive heat losses.

            Installing the main on posts just above the ground surface while satis–

    factory under certain conditions is inconvenient if the route necessitates

    crossing highways and railroad lines, as the main must be depressed under

    or carried over such traveled ways.

            The overhead pole-line type of installation has its merits under certain

    conditions and, as in the previous method, requires no trench excavation and

    is open to inspection at all times. It does, however, establish limiting

    clearances at highway crossings and does not appear to be entirely suitable

    for a military installation.

            In those regions where extremely cold temperatures are the rule or perma–

    frost is encountered, some means must be adopted to prevent water and sewer

    mains from freezing. Heat lost from the steam mains, if in close juxtaposition

    with the water and sewer mains, will permit maintenance of the required above–

    freezing temperatures. The type of construction best adapted to this method

    of installation consists of a suitably sized buried conduit containing shelves,

    hangers, or other devices required in supporting the several utility mains.

    This buried conduit or pipe gallery is the so-called “utilidor.” As inferred

    above, it will vary in cross-sectional dimensions to suit the size and number

    of pipes to be carried and, as a consequence, may be of the larger “walk-through”

    type (Fig. 6), the “crawl-through” type (Fig. 7), or the minimum-sized service

    structure. In most cases a sewer will be among the utilities carried. A

    study of the entire system will determine the relative economies of gravity

    flow and pumping in total or in part. Proper manhole placement and ability

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    to remove covers on the utilidors is a prime requirement to take care of

    major repairs and overhaul work. This design feature is particularly

    important for crawl-through type and minimum-sized units of utilidor con–

    struction. It should again be stressed that all important factors that

    need periodic attention, such as condensate or other pumps, expansion joints,

    traps, motors, and controls, should be located at manhole openings in the

    crawl-through type where they are most readily accessible for check and

    repair. Furthermore, in crawl-through type of utilidors, special care must

    be taken that, in the design and construction, full regard for further proper

    access for inspection and minor repair is given. Unless this point is stressed,

    installation people will so block the areas with supports and hangers that

    it becomes almost impossible to inspect the lines.

            If it is anticipated that permafrost will be encountered along the route

    of a proposed utilidor system, test pits should be excavated to determine

    soil types and their suitability as foundation material and the possible need

    for waterproofing the exterior of the structure. Should explorations indicate

    that the subsoil will be somewhat unstable when thawed, provision should be

    made for removing it to a minimum depth of two feet below the foundation and

    replacing it with a thoroughly compacted layer of well-graded granular material.

    This will not only provide a suitable foundation, but will serve, to a certain

    degree at least, as an insulating blanket in preventing excessive thawing in

    the permafrost.

            Should the permafrost be extremely fine grain, the bulk of which passes

    200-mesh sieve when thawed, it may be impossible to provide a suitable founda–

    tion for the utilidor except by means of piles. Such an installation might

    be so costly that overhead steam lines will result in the most practicable


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            The material from which it is constructed should be such as to insure a

    long-lived structure impervious to the infiltration of ground water. A

    reinforced-concrete structure appears best to satisfy these requirements.

    Various cross sections may be developed to suit the needs of the particular

    project. These may be rectangular, semicircular. circular, or parabolic in

    shape. The rectangular design has invert and side walls of poured-in-place

    concrete and a precast sectional cover. The invert and side walls to the

    spring line of the semicircular sections are of monolithic concrete con–

    struction, while the removable top is nothing more than a half section of

    centrifugally spun concrete pipe of standard length. The full circular

    design is standard centrifugally spun concrete pipe split along the hori–

    zontal diameter. These split sections can be manufactured with standard

    pipe plant equipment requiring only slight alterations to the forms. The

    parabolic section has a poured-in-place invert and a precast cover of vacuum–

    processed concrete. The semicircular, circular, and parabolic sections are

    each constructed in part or wholly of precast units. This has one definite

    advantage in that the various units may be constructed during the winter

    months when outside work is not possible and reduces to an appreciable degree

    the field labor contingent. However, they require a considerable plant invest–

    ment and, unless a number of miles of an identical size structure are involved,

    the unit cost per foot of each will exceed the unit cost per foot of the rec–

    tangular section. Dimension and cross-sectional area of the latter may be

    enlarged or decreased as required without regard to plant investment.

            Temporary Utilidors . The above considers permanent types only. During

    the construction period or where mobilization-type structures are used, it

    is often necessary to provide an installation of temporary or semipermanent

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    design. For strictly temporary use for one or two seasons, a surface-laid,

    insulated wooden utilidor will, in all probability, prove to be the most

    economical type of structure. For mobilization-type construction, the utilidor

    might be a combination of concrete and treated timber, resulting in a design

    comparable in durability to the buildings served. In a case of this kind,

    the distribution system also would be designed with a minimum of refinements

    consistent with general requirements.

            Central Steam Distribution vs. Individual Space Heating . The initial

    investment required for the installation of a steam power plant and utilidor

    distribution system is high. The only alternative lies in the installation

    of separate heating units for each individual structure. A careful review

    of the facts in the case, i.e., additional operating and maintenance labor

    required and means to keep the sewer and water supply systems in operation,

    indicates the pattern to be followed. If for some reason or other, central

    steam distribution is not provided for a particular area, the water and sewer

    mains can be carried in a much smaller utilidor heated by steam tracers fed

    by a small boiler plant provided for this express purpose. This is a perfectly

    satisfactory system mechanically; however, studies will probably show the

    annual cost of service of such a system will exceed the annual cost of

    service of an installation including central steam distribution and, in

    general, indicating the economic advantages and desirability of a central steam

    heating and distribution plant.

            Radiant Heating . While the detail of heating distribution is now

    recognized as having an important place in space heating, its use in the

    subarctic is of even greater importance than might at first be suspected.

    Pioneering in its use has been accomplished. For large g h angars, warehouses,

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    shops, and such structures, careful consideration must be given to its use.

    A problem arises in those regions where permafrost exists, but generally by

    careful treatment of the individual case, a solution can be found.




    Ventila f t ing Systems

            Experience has shown that adequate ventilation of dwellings located in

    arctic or subarctic regions is an important factor in maintaining the good

    health and comfort of the occupants and is of particular importance in bar–

    racks, mess halls, hospitals, schools, and other permanent-type structures

    where large numbers of people assemble.

            Ventilation may be defined briefly as a process by which air is supplied

    to and removed from an enclosed space by natural or mechanical means. In the

    former, activation is by means of wind forces and the temperature differential

    between the inside and outside air. Operating efficiency is variable in

    accordance with the activ [ ?] a ting forces.

            Manually controlled ventilation systems for the smaller barracks, ware–

    houses, shops, or industrial buildings can be effected by the same means as

    those commonly used in more temperate regions; windows usually fitted with

    adjustable storm sash, roof vents, and simple fans are adequate for the purpose.

    Screens for all such openings are just as much a necessity in the Far North for

    insect control as elsewhere. However, for the more scientifically designed

    larger structures — barracks, mess halls, shops — the use of such elementary

    ventilation in the Arctic or Subarctic is generally limited to providing a

    proper circulation of air in unheated attic or similar spaces and thus

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    minimizing the possibility of moisture accumulating in these areas through

    excessive condensation. A system of mechanical ventilation is, as the name

    implies, so designed as to be efficiently operable in entire independence

    of natural forces and may consist of any number of refinements up to the point where

    it may be more applicably called “air conditioning.” As considered here, it

    will consist of intake and discharge vents, supply and exhaust fans, air

    heaters, humidification equipment, and all necessary controls. Air cooling

    will, in all probability, be required for limited use in some hospital rooms

    for summer use; however, this can be treated as a special problem and its

    control can be effected by packaged units independent of the main ventilating


            The various factors serving as a basis for the design are the climatological

    conditions described in Section I, the location and orientation of the building,

    its type of construction, and the purpose for which it is to be used, all of

    which introduce a number of interrelated variables. In general, these factors

    differ in no way from those encountered in the States, except for the extremes

    in temperature, and, accordingly, designs should be developed along similar


            Barracks, mess halls, kitchens, and other buildings all require air

    changes at varying rates. Barracks should have a minimum of 4 changes per

    hour with 25% fresh air or 10 c.f.m. per person with 25% exhaust. Large

    mess halls will require 10 changes per hour with 50% fresh air, and kitchens

    10 to 20 changes per hour of 100% fresh air. During periods of extreme cold

    with an outside temperature of, say, 50°F., the heat required to warm the

    cold air to a room temperature of 70°F. is substantial and a heavy load is

    placed on the heating system. This condition can be alleviated by the simple

    expedient of recirculating the air and cutting the fre x s h air intake to 5 to 10%.

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    As temperatures rise, fresh air intake may be increased to normal.

            To insure indoor atmospheric conditions conducive to good health and

    comfort in cold climates, the ventilation system should be designed to include

    delivery of air with the proper moisture content. In a temperate climate, 30%

    relative humidity at 70°F. is the generally accepted minimum requireme u n t;

    however, during extended periods of extremely cold weather, relative humidity

    should be lowered to 20% to prevent excessive condensation, but should not

    be allowed to go below this point in the interests of good health. With atmos–

    ph a e ric temperatures of −50°F., the relative humidity of outside air may be

    as high as 80 [ ?] o r 90%, but, due to the low vapor pressure at this temperature,

    actual moisture content of the air for all practical purposes is nil. Air

    taken into the ventilation system at this temperature and warmed to 70° F.

    without moisture being added will have a low relative humidity, probably

    less than 5%. Humidification of the ventilating air, therefore, is an essential

    factor in a ventilating system designed for cold countries. Hospital operating

    rooms require special attention and should be provided with a complete year–

    round air conditioning, permitting a minimum of 12 changes of air per hour and

    a relative humidity of 55%. Maintaining the humidity at this point tends to

    reduce explosion hazard and is found to be more satisfactory for the patient.

    Conversely, during the summer months, cooling and dehumidification will be

    required at times. In all of these rooms where high relative humidities

    are maintained, double-glazed sash will be necessary to prevent condensation.

            In this connection, it is pointed out that ordinary building materials

    are vapor permeable and, because of the wide difference existing between

    vapor pressures at + 70°F. and −50°F., there is a natural tendency for these

    un h b alanced pressures to equalize. The warm interior, having the higher vapor

    pressure, loses moisture at a rate in accordance with the vapor permeability

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    factor of the wall structure. This condition may be eliminated by incur–

    porating a vapor barrier in the building design. This is nothing more than

    a layer of highly impervious material installed on the warm side of the

    exterior, usually directly under the plaster, wallboard, or other interior

    wall finish. In the absence of an effective vapor seal, moisture will con–

    dense and freeze within the walls and under roofs of buildings in frigid

    climates; alternate freezing and thawing causes the buildings to deteriorate



    Refrigeration Systems

            On first thought the need for providing refrigerated storage in arctic

    or subarctc or subarctic climates appears ridiculous; however, a hasty review

    of the factors and conditions involved will readily read just any such impression

    and bring out the realization that refrigeration facilities are quite important

    in the storage of foodstuffs in the Far North as in the tropics. It is true

    than an individual might make u a s e of the natural conditions obtaining in the

    permafrost regions or where glaciers are available, and many instances of

    such use can be cited. So far as can be determined, the planned use of the

    permanently frozen soils of the North for refrigeration purposes was first

    seized upon by Europeans. The Eskimos and other northern natives were

    accustomed to diggin s g shallow pits for storage of food down to, but not into,

    the permafrost; cold cellars of this type provided only partial refrigeration,

    retarding but not preventing decay. (See “Natural Cold Storage.”) Ice houses

    to keep food chilled during warm seasons have in isolated communities been

    employed for winter storage as well; a common sight in the North is the trapper’s

    cache wherein he keeps his fresh meat frozen and safe from roaming animals

    throughout the winter. Root cellars (Fig. 8), frequently used on farms in the

    northern states, are also a common means of winter storage for vegetable crops.

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            However, in view of the close temperature and humidity control required

    in storing large quantities and varieties of foodstuffs over variable periods

    of time, it is commonly believed considered that adaptation of natural conditions on a

    large scale is not a practical method of approaching the problem. (But see general article “Natural cold Storage.”) As a

    consequence, in all established communities and camps, cold-storage plants

    and their operation are a common facility, as a result of the importance of

    fish and gam s e as food to Alaskans, together with the need of bulk buying

    for economy reasons. Probably a [ ?] g reater percentage of people in the Territory

    have frozen-food lockers than elsewhere. (There are dissenters to this

    pessimistic view of the adaptability of natural conditions to large-scale

    refrigeration — see “Natural Cold Storage.”)

            Refrigerated storage must provide both freezer space and cold rooms with

    control l ed temperatures of 0° to 10° F. and 30° to 40° F., respectively, and

    should include facilities for manufacturing ice. The design should have

    adequate floor area and hea r d room to insure proper cold-air circulation.

    Stored products should not be stacked closer than 12 inches to the walls of

    the room or to an adjacent pile, and no higher than 3 to 4 feet from the ceiling.

    Deducting aisle space and column areas further reduces the net usable storage

    area to about 40% of the gross room area. Factors affecting the design include

    climate, transportation facilities, and the quantities and types of foodstuffs

    to be refrigerated. These factors are basic and must be considered regardless

    of location. In Alaska the uncertainty of transportation facilities and the

    need for importing foods will in all probability have the greatest effect on

    design in the matter of quantity storage and space requirements. Auxiliary

    heating facilities must be provided for cooler rooms in arctic installations

    to insure against freezing during extremely cold weather. Other than the above,

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    designs for refrigerated storage in Alaska will be identical with those for

    use in the United States.

            Humidity control is of extreme importance in any cold-storage plant.

    Excessive humidity will cause the stored products to mold and too little

    moisture in the air will dry them up. Experienced packers and cold-storage

    operators have found that the best humidity is obtained when the temperature

    of the evaporator coils in the cooler rooms is held from 4 to 5 degrees below

    the room temperature. Increasing this difference will dry up the air, and

    decreasing the difference will increase the humidity.

            Different foods require different temperatures and humidities if they

    are to be held in good condition over long periods of time; consequently,

    separate individually controlled cooler rooms should be provided. Of course,

    it is not feasible to hold to this design criterion literally. Those foods

    whose optimum storage temperatures vary but little may be stored together

    and the cooler room held at a compromise temperature and humidity without

    adverse effect.

            Where refrigeration of a greater capacity than that afforded by the

    mobile “reefer” or “walk-in” unit is required as a servicing facility for

    temporary or mobilization-type units, it is believed that a prefabricated–

    type structure warrants every consideration. They can be designed to meet

    all ordinary refrigeration requirements and can be erected and placed in

    operation in a matter of days.

            The use of material available in any specific locality is very desirable,

    both for helping in the developing of the region and also for effecting saving

    in transportation. Several important materials that have interesting possi–

    bilities [ ?] as insulating materials are the pumice or volcanic-ash deposits

    found in certain regions and the tundras or muskegs that cover the land.

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    The latter material is the natural food of vegetation-eating wild life, but

    it is abundant and has excellent value as an insulation. It has been observed

    that under several feet of snow and several feet of such vegetation, unfrozen

    ground water has been found during a time when temperatures for a period of

    over three weeks ranged from minus −50° to −70° F.


    William Everett Potter

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