Final answer:
Air-to-air heat pumps without auxiliary heat provide air to the registers at approximately 85°F or less. The efficiency of such heat pumps can be evaluated using their coefficient of performance, which is calculated based on the temperatures of the hot and cold reservoirs in Kelvin.
Step-by-step explanation:
The question asks about the temperature of air supplied to the registers by an air-to-air heat pump operating without auxiliary heat. The correct answer to this question is that air-to-air heat pumps provide air to the registers that is approximately 85°F or less.
Heat pumps transfer heat by absorbing heat from a cold environment and releasing it into a warmer one. The efficiency of a heat pump is often measured by the coefficient of performance (COP), which is the ratio of heat output to work input. For the ideal heat pump operating between 5.00°C and 35.0°C, the COP can be calculated using the formula COP=rac{T_{hot}}{T_{hot} - T_{cold}}, where T is the absolute temperature in Kelvin. Similarly, for other scenarios, the COP and related performance metrics can help determine the temperatures and energy efficiency of heating or cooling systems.