Document bwL8LKXVbKpjrpVZXdQ9Nyp6

American Society of Heating and Ventilating Engineers Guide ' , 2. For ducts in outside walls or attics, or other exposed places, allow n<i linear foot of uninsulated duct. ' u-25 F,, 3. For ducts run underground an allowance shall be made based on the loss of the duct, assuming the average temperature of the ground to be SSfr Heat Supplied Heating Units and Washer The following cases may arise in practice: A. The heating of the building is done entirely by means of a central fan of the air being drawn from the outside. B. Similar to A, except that all of the air is recirculated. C. A portion of the air is recirculated, and the remainder is drawn in from the - D. Air at the same temperature is to be delivered to all the rooms. A constant humidity is.maintained in the building arid all of the air circulated is drawn from the briifditig. (Not applicable to the heating of various rooms where individual of each room is desired.) E. Outside air, return air, and by-pass air are used with the reheater located inki pass air chamber. " "i F. Arrangement of apparatus where individual control of the temperature for room is required in conjunction with air washer equipment to maintain a conS relative humidity in the rooms: The air washer is provided with, a water heater.fory spray water, capable of fuljy saturating the air, A section of preheater may be used f this purpose in place of Che water heater. With this arrangement and with a unifa! temperature of air entering the rooms, it is impossible to maintain the same room tet perature throughout the building because the weight of air to be delivered to each room is determined and fixed by the ventilating requirements. ; In analyzing these cases, the following symbols will be used: H = heat loss of the room or building, Btu per hour. Hi = heat to be supplied to the reheater coil, Btu per, hour. , Hi = heat supplied tempering coiI,-or.tempering coil-tand, preheater^ Btu per,bout- Hi = heat supplied air washer by waterheafer, Btu-perhour. - Ht = heat to be supplied booster coil, Btu pet hour. 1 M - weight of air to be introduced into the roqm or building, pounds per hour. J iAfr = weight of recirculated air, pounds per hour. ' ' Mb = weight of air by-passing washer, pounds per hour. Mo = weight of air drawn in from outside, pounds per hour. to -- mean temperature, of outside air, degrees Fahrenheit. t -- mean air temperature to be maintained in the room or building, degree Fahrenheit. <i = mean temperature of the air entering the reheater coil. h = mean temperature of the air leaving the reheater coil. tz = temperature loss in the duct system. ty = temperature of the air leaving the duct, outl/ets. tx = average temperature of air entering tempering coil. . .ty, = temperature, of, air entering washer. . .: '0,24 = specific heat of air at constant pressure. /Steam Control Valve j ^Control Valve uer-- v'Air Leaving Fan at ty jj^Pulley ' Louvres > ' - *--7- Wp 'Outside Wall'i: - Gy-pass Damper Foundation / Floor Line Heating Unit and Fan Arranged for Outside Air Circulation (Case A) l- F'io.3. ..._ "y. " /p:,, 3) All of the air circulated to be drawn from outside the building, in - " ' ^*J*hich case tx - toH, = 0.24 (f, -- to) Mo Hi = 0:24 (h - h) ifo Jc.nmblt 4 The heat loss ff for a certain factory building is 700,000 Btu per hour, Srei mMn inside temperature t to be maintained is 65 F. The assumed outside air tem0 F; fe = .0, ty = h and is assumed to be 140 F. The temperature frSgthe tempering coil is assumed to be 35 F. Required, Hi and Hi. From Equation 4, ' ' .......................................... M = 700,000 0.24 (140 - 65) = 38,889 lb per hour. - ;, ___ _ = o.24 X (35 - 0) X 38,889 = 1:326,667 Btu per hour. = 0.24 X (140 - 35) X 38,889 = 980,003 Btu per hour. .+.ffi 326,667 + 980,003 = 1,306,670,Bt;per hour. .-fei'-J. ,'"V- `. C. - ssStfc?. Th? ` 1 * * ^Steam1 ^/Automatic Valve,. _ Air Leaving Fan at ty L- Air Returned -from Heated Space Fan. Fig. 4. fl ' ` ; ' ELEVATION ' . ',. Arrangement for Recirculation {Case B) yt' '(Fig. 4) AH of the air is to be recirculated, in which case h t. Mr = 38,8891b , . Mi = 0.24 (<, - ti) Mr. Hi = ,0.24 (140 - 65) X 38,889 = 700,000 Btu per hour. r .^?';This Sample illustrates the saving in fuel consumption'by'the recir- Aailation of the air. The heat to be supplied the apparatus is the same as :Sfthatrequired for a direct system of-heating and is:eq ual to the heat loss Jof the building: (iifi =11), in the example. 700,000 ;Btu per rhour as compared with 1,306,670 for>. Case A. tr:, r 367