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Energy analysis of residential structure space conditioned by heat pump and furnace using computer simulation

University of British Columbia

An energy simulation program, named RHECAP (Residential Home Energy Consumption Analysis Program), for residential structure space conditioned by a furnace and a heat pump has been developed. The program calculates the hourly cooling or heating load imposed on the furnace or heat pump and then the energy input to the furnace or heat pump to satisfy the load for every hour of every day of a condensed year. The condensed year consists of thirty-six days; a month is represented by three days. The hourly cooling load is determined by using a method designated as "Time-Averaging with Shift". This method has been developed from time-averaging principle and uses a different set of parameters, time-averaging period and shift amount, for different energy sources. Each hourly load of a day is obtained by summing the arithmetic average of the radiant heat gains of a number of preceding hours and the convective heat gain of the current hour. This gives the daily load profile which is then shifted to yield the final load profile. This method accounts for the building heat storage effect in converting instantaneous heat gain to the cooling load. A polynomial equation which expresses the furnace efficiency degradation with the drop of the furnace load has been developed. This equation and the furnace performance at steady state condition are used to represent furnace performance for the entire range of operating conditions. The same equation can be used for furnace units of all different capacities. Six linear equations that represent the non-dimensionalized heat pump performance, the output rating (heating and sensible cooling) and electricity use, have been developed. The equations are functions of the outdoor enthalpy. These equations only require the heat pump performance at the outdoor temperature of 35°C (tonnage of heat pump is quoted under this condition) to represent the heat pump performance for the entire range of outdoor operating conditions. The six equations can be used for heat pumps of different capacities from different manufacturers. A simple method of selecting a yearly condensed weather data has been developed. The condensed weather data consists of three days of actual weather information for each month. The weather information is used to determine the cooling and heating load contributions of weather dependent sources and heat pump performance. The program results are compared with the results of two existing programs using an existing and a fictitious residential structure in Vancouver to validate the program. The validation of the program seems to indicated that the program provides acceptable results and the simulation methods used are valid.

Text

2010-04-22

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http://hdl.handle.net/2429/24066

Mechanical Engineering

University of British Columbia

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