Thermoelectric Sub Cooler for Cold Climate Heat Pump

Summary

Conventional cold climate heat pumps use a vapor compression system, designed to maximize heating capacity at very low ambient temperatures (from 17°F to -15°F). But it is complicated and expensive. This invention is a thermoelectric heat pump that goes inside the indoor air handling unit of a regular heat pump for building space heating. The assembly consists of thermoelectric modules sandwiched between microchannels that transport refrigerant. The technology extracts unusable heat and boosts it to a useable temperature and location, adding capacity and increasing efficiency.

Description

The liquid refrigerant temperature leaving an indoor heat exchanger cannot be lower than the indoor air temperature. The big temperature difference between the indoor air and ambient air causes high vapor quality entering the evaporator which decreases latent heat to absorb source heat from the ambient. Further, a large percent of vapor entering the evaporator cycles back to the compressor without absorbing heat from the outdoor air, wasting compressor power. To improve efficiency, the key is to further cool the liquid refrigerant before it enters the evaporator. This invention places a thermoelectric heat pump device inside the indoor air handling unit of a heat pump. The device is powered by electricity from the grid. The assembly consists of thermoelectric modules sandwiched between microchannels that transport refrigerant and extracts unusable heat. The cold side extracts heat from refrigerant as it leaves a subcooler heat exchanger. The hot side discharges heat to refrigerant leaving a condenser. This refrigerant exits the condenser, then enters the hot side microchannel where some of the refrigerant is evaporated. Then it flows back to the subcooler which discharges the heat pumped by the thermoelectric modules back to the indoor air.

Applications and Industries

• HVAC industry
• Residential and commercial homes and buildings, primarily in cold climates

Benefits

• Increases capacity and efficiency of cold climate heat pumps
• Extremely compact, uses refrigerant convective heat transfer on both sides of the thermoelectric device
• Highly controllable
• Lowers the refrigerant vapor fraction entering the evaporator
• Does not increase compressor discharge temperature (unlike some alternative approaches to boosting cold climate heat pump capacity)