Document 44pXg6rNb34VnX983rGe5bz4x

998 CHAPTER 48 1950 Guidf'JPf > heat from this source is transmitted to the coil through the plate'rather than from the heated air surrounding the coil. Otherwise, only part of the heat enters the coil, the balance being transmitted through the glass. Design data given in Table 11 may be used withjudgment in selecting the size of solar heater coil and box for a particular application. These data are based on consumptions of 30 and 40 gal of hot water per day per person. DOMESTIC HOT WATER BY HEAT PUMP Domestic hot water may suitably be obtained by using a heat pump installation. The hot water heater may be either a heat exchanger in stalled just ahead of the compressor of a heat pump installation, or may be a self-contained domestic-water heat pump. Various designs of self-contained domestic water heat pumps are avail-' able, and one particular arrangement is shown iri Fig. 14. Fig. 14. Heat Pomp Abbangement fob Hot Wateb Supply Although the first cost of domestic hot water heat pumps is somewhat high, they have the advantages of eliminating products of combustion, odors and soot, and not needing a chimney.A further advantage is that they may be used for cooling purposes. With a coefficient of performance of 2 to 3, water temperatures of 140 to 150 F may be obtained.5, REFERENCES 1 Methods of Estimating Loads in Plumbing Systems, by R. B. Hunter {National Bureau of Standards,Report BMS65, 1940). Plumbing Manual, Report of the Sub committee on Plumbing, Central Housing Committee on Research, Design and Con struction {National Bureau of Standards, Report BMS66,1940) . Water-Distributing Systems for Buildings, by R. B. Hunter {National Bureau of Standards, Report BMS79,1941). - * Water Distributing Systems for Buildings, by R. ,B. Hunter (National Bureau of Standards, Report BMS79, p. 6-9). (Charts extended to flow of 0.39 gpm.)> * Plumbing Practice and Design, by Svend Plum (John Wiley anid Sons, Inc.,: 1943)'. 4 Hot Water Requirements, by M. B. Mackay. {Modem Sanitation, August; 1949, " Vol. 1, p. 30). * Progress Report on a Heat Pump Water Heater, by P. Spdrn and E..R. Ambrose {Heating and Ventilating, February, 1949, Vol. 46, p. 78). BIBLIOGRAPHY Laundry, Kitchen and Hospital Equipment, by H. C. Russell (A.S.H.V.E. Tbans- actions, Vol. 35,1929, p. 45): . ., > Water Consumption, .Cost and Savings, by G. C. St. Laurent (American Hotel Association, Hotel Engineering, Vol. 1,1940). Water-Supply Piping for the Plumbing System, by F. M. Dawson and A. A. Kalinake (Technical Bulletin No. 3, National Association of Master Plumbers). Use of Solar Energy for Heating Water, by F. A. Brooks, Smithsonian Institution, Washington, D. C. - 'i CHAPTER 49 INSTRUMENTS AND MEASUREMENTS T oerature Measurement, Pressure Measurement, Air Flow Measurement, Air c]jange Measurement, Humidity Measurement, Heat Transfer Through ` Building Materials, Evaluation of Thermal Environment, Combustion Analysis, Smoke Density Measurements, Determination of Air Contaminants, Sound and Vibration Measurements T TEATING' and air conditioning engineers and technicians require r"l instrumentsfor both laboratory and field use and somewhat more pre cision is attainable and essential in the laboratory, where research and de velopment are undertaken, than in the field, where acceptance and adjust- ment tests are conducted. Some instruments have attained an adequate state of development, while others fall far short of the desirable. For inf stance temperatures can now be measured readily with ample accuracy for most purposes, while a convenient and precise method for determining or comparing the dustiness of atmospheres is lacking, and improvement in existing hygrometers and humidity controllers is essential. Codes and standards covering different types of heating and air condi tioning devices and apparatus have been promulgated by various authori tative organizations, and instruments essential for performance or com pliance testing are enumerated in the relevant publications.^ * * * The present purpose is..to discuss the use and^characteristics of the more im portant instruments. , f, V - . TEMPERATURE MEASUREMENT5-5 ; Thermometers / ' '. Any device capable of indicating temperature , is a thermometer, but in common usage the. term thermometer without qualification has come to signify the ordinary mercury-in-glass temperature indicating device. This type has a useful range from --40 F, the freezing point of mercury, to.about 1000 F, at or near which the. glass usuallyjsoftens. Lower.temperatures can be measured with alcohol-filled thermometers for, which the range is about --.94 F to +248 F, The better, thermometers have their scales; either Fahrenheit or Centigrade, etched with acid into the glass which forms their stems. ; The probable error for etched stem thermometers,is plus'or minus one scale division, and calibration is desirable for much test work; Thermometers are calibrated during manufacture at not less than two temperatures--the freezing and boiling points of water--and .calibration is often accomplished with the instrument completely immersed in a bath at the known temperature. The intervening scale divisions are then ap7 plied to the .stem. When such a. thermometer is used with the stem-in-: completely: immersed, a correction known as the stem correction is neces sary for accurate measurements, and its magnitude is usually computed by means of the following formula: where K = 0.00009 D {ti - t.) . V ,. . K = correction to be added, Fahrenheit degrees, 999 .. .. (1)