Document B8D6Y8zdVobZxMMrBXjo5YRVj

544 CHAPTER 36 1960 Guide War%c5>. f?3Zta?%*<IYiJPeii with Vaponzmo Pot-Type Burn er*) CS109-44 Solxd-Fuel Burning Forced Aw Furnaces, CS113-44 Ou-Burmng Floor Furnaces Equipped with Vaporizing PotType Burners (National Bureau of Standards Commercial Standards). a."Amf?car* Standard Installation oj Gas Appliances and Gas Ptpmg (American Standards Association, Z2130-1959). " Comfort Heating (American Gas Association, 1938, p. 71). C. G. Segeler: Sizing of Chimneys and Flues Used for Gas Appliances (American Gas Association, Sixth International Gas Conference, 19S5). "N. D. Mitchell: Fire hazard testa with masonry chimneys (Rational Fire Protection Association Quarterly, October 1949). *S- E<nuo: Chimneys and draft (Winter Air Conditioning, National Warm Air Heating and Air Conditioning Association 1939, Chapter 32). CHAPTER 37 ESTIMATING FUEL CONSUMPTION FOR SPACE HEATING Bases of Fuel Eirirnafes; Efficiency of Utilization; Calculated Heat Loss Method.- Computation and Application, Short Methods for Estimating Heat Loss; Degree-Day Method: Computation and Application, Unit Fuel Consumption per Degree Day, Estimating Consumption for Various Fuels, Degree Day as an Operating Unit; Industrial Degree Days; Maximum Demand and Load Factors IT IS often necessary to estimate the anticipated heat re the heat in the fuel is used. Efficiency can be defined in quirements and fuel consumptions of heating plants for a variety of ways for various purposes, and the values either short or long terms of operation. These quantities can in any given case can vary widely depending on the con be much more difficult to calculate than design heat loss or ditions. For estimating purposes, as will be shown later, it required system capacity, since they involve essentially the is the efficiency of utilization of the fuel over the calculation summing up of the net result over the period in question of period which is wanted. This is distinct from furnace efficiency the influence of many factors which may vary greatly with which expresses the heat delivered by a furnace unit as a per time. It will seldom be possible to predict with any great ac centage of the heat provided in the fuel and which is the curacy the way in which all the factors involved will vary efficiency normally used in describing the performance of throughout the prediction period. In addition to this, the cal a unit under rated, or stated, load conditions. It has been culations required to take all such variations into account shown, at the University of Illinois for example/ that in the become very involved. For these and other reasons records case of a dwelling with an inside ebimney, as much as 35 of past operating experience, when these are available, pro percent of the beat delivered to the chimney which is nor vide the most reliable and usually the most accurate basis mally considered to be a loss so far as efficiency of the fur for the prediction of future requirements. nace is concerned may be delivered to the house through the Records of past heat requirements or of fuel consumption heated chimney walls. This recovered heat amounted to as of a particular building are a better basis for estimates than much as 12 percent of the heat required by a house. Much are averages of records from similar buildings. In the-absence of this recovered heat may be available for heating. It has of past records for a particular building the data from sim been said in connection with the same study that at times ilar plants in the same locality may have to be used. Averages only about 50 percent of the heat utilized by a house was of consumption figures taken from many types of plants in supplied by radiators, while the other 50 percent of the many types of buildings in various localities can only pro heat utilized was supplied from such sources as chimney, duce an average estimate which may prove to be inaccurate piping, boiler jacket and smoke pipe, people, lights, etc. A when applied to a particular building. summary** * of many tests in two research residences at the Where unusual operating conditions exist due to factors University of Illinois using many fuels and systems give such as excessive ventilation,, abnormal inside temperatures, values of 67 to 90 percent for overall house efficiency (the and heat gains from external sources, or where, in the ease of ratio of the heat loss from the structure to the heat input proposed buildings of unusual design, no information is avail to the unit for an average day). able regarding former consumption, it is necessary to estimate The efficiency of utilization of the fuel burned can at times fuel consumption from the computed heat losses. be relatively very high for houses. It can also vary quite In preparing fuel consumption estimates it is well to real widely from one house to another because of variations in ise that any estimating method used will produce a more chimney location and design, in the utilization of heat lost reliable result over a long period operation than over a to the basement from the heating unit and smoke pipe, and short period. Nearly all of the methods in common use will for. other reasons. The efficiency of utilization may vary give trustworthy results over a full annual heating season, with time of year as the average load on the furnace varies. and in some cases such estimates will prove consistent within Some of the reasons for this in the case of intermittently- X' themselves for monthly periods. As the period of the estimate fired oil furnaces have been demonstrated.* is shortened, there is more chance that some factor not taken In buildings other than houses the efficiency of utilization into account directly in the estimating method will deviate of the heat supplied in the fuel may also vary widely. There from its long-time average value, and thus lead to serious will, in general, be less tendency in many larger buildings error in the predicted beat requirement. toward effective use for heating purposes of the heat which is normally lost from chimney, furnace, and piping surfaces, EFRGENCY OF UTILIZATION and efficiency is seldom likely to be as high as in the case of many houses. Any method of estimating fuel requirements based pri The average fuel consumption of various types of ap marily on calculation of beat losses must, of necessity, also proved gas-fired equipment has been obtained from a large take into account considerations of the efficiency with which number of heating systems.1 Corresponding efficiencies of 545