Abstract
This study compares the performance of a single gas- fired conventional domestic space heater with that of the same conventional heater in combination with a smaller auxiliary heater. The auxiliary heater could be a solar heater or could obtain its energy from more conventional sources. The auxiliary heater is presumed to have a shorter time constant than the main furnace. As room temperature falls below the present temperature, the auxiliary heater turns on before the main furnace, but turns off when the main furnace comes on. In the study the following param eters were varied:
Hysteresis of the main furnace's thermostat Hysteresis of the auxiliary heater's thermostat
Time constants of the controller, main furnace, and auxiliary heater
The size (heat output capacity) of the auxiliary heater as a percentage of the size of the main furnace.
The outputs recorded were temperatures variations of the room air and the cycling time of the system. In each case results are plotted as a function of the relative size of the auxiliary heater for 3 values of one of the time constants, the other two time con stants and the hystereses of the thermostats being held constant. Operating conditions were a set point temperature 70°F (21°C) for room air and an outdoors air temperature of 0°F (-18°C). In all cases examined the system with the auxiliary heater produced more uniform room temperatures. Shortening the time constants of the controller and the auxiliary heater reduced variations in room temperature.
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