Water-to-air heat pump

Measures SH and SI are hydronic water loop systems with water-to-air heat pumps. These systems also offer energy savings over the base case, but have an incremental cost over the base case. Other than the system type, these measures are the same as SE and SF, so either payback period is immediate for similar reasons. 

Outdoor air is treated and pre-conditioned by a central water-to-air heat pump. The outdoor air is delivered into the return air plenum of the zone heat pump units. A total enthalpy wheel can reduce the energy consumed for treating outdoor air. 

The water-to-air heat pumps are available in the market from various manufacturers ranging in capacity from 1/2 tons and upward. Manufacturers include ClimateMaster, McQuay, Trane, Carrier, Waterfiirnace and Florida Heat pump. 

Figure 16. Conventional water loop heat pump system with fresh air heating by water-to-air heat pump...

Most refrigeration systems are essentially the same as the heat pump cycle shown in Fig. 6.37. Heat is absorbed at low temperature, servicing the process, and rejected at higher temperature either directly to ambient (cooling water or air cooling) or to heat recovery in the process. Heat transfer takes place essentially over latent heat profiles. Such cycles can be much more complex if more than one refrigeration level is involved. 

Simplified Cycle. A simplified fossil steam cycle appears in Figure 19. The water accumulates in the bottom of the condenser, called the hotweU. It goes through a feed pump to pressurize it. The pressurized water passes through one or more feedwater heaters, which raise the temperature. The water then enters the boiler where heat from the fuel converts it to steam. The steam expands through the engine, usually a turbine, which extracts work. In the middle of the turbine some of the steam is extracted to supply heat to the feedwater heater. The remainder expands through the turbine and is condensed. The rejected heat is carried away by the condenser coolant, which is usually water, but sometimes air. The condensed steam then returns to the... 

The furnace blower or boiler circulator pump starts up to send heated room air or hot water through the ducts or hot water pipes to the steam radiators, or hot water baseboard units, or individual room air registers located throughout the house. When the thermostat is satisfied that the room temperature has reached the set point, the burner shuts off. In furnaces, the blov er continues to run a few seconds until the air temperature drops to about 90° F, then the blower also shuts off. The furnace blower may come on again before the next burner start-up to purge heat out of the furnace, particularly if the fan has a low turn-on set point. The cycle... 

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