Vortex Enhanced Direct Contact Heat Exchanger for Geothermal Cooling

In 2005, commercial and residential Heating, Ventilation, and Air Conditioning (HVAC) systems represented 518 billion kWh of energy consumption in the United States, which amounts to 8% of the total energy produced that year. In addition, producing this power resulted in the release of 465 MMTCO2e of greenhouse gases. By reducing the energy demand of air conditioning systems, the US can realize a significant reduction in consumer energy costs and greenhouse gas emissions. ACT is developing a Vortical-flow, Direct-contact Heat Exchanger (VDHX) for integration with residential and commercial HVAC systems. The primary objective of this device is to reduce the energy consumption of these systems by exceeding the energy efficiency of traditional finned-tube heat exchangers. This improvement in energy efficiency will stem from a reduction in coolant to air temperature difference, which will reduce compressor energy consumption, and a reduction in pressure drop through the heat exchanger, which will reduce fan power consumption. By the end of the Phase I program, ACT successfully fabricated and tested a VDHX demonstration unit that cooled air from 33 C to 15C using an inlet water temperature of 10C. The unit provided 8 kW (2.3 tons of refrigeration) at 735 CFM. To determine the impact of this performance on HVAC energy consumption, ACT developed a residential cooling model, based on thermodynamics and the Residential Loaf Factor method, to study HVAC performance at 70 locations across the US. According to this analysis, the VDHX can provide 33% to 60% energy savings over a traditional GSHP system and 30% to 50% over a traditional Air-Source Heat Pump (ASHP). ACT will build on the Phase I progress by first optimizing the VDHX design. We will work with our university and commercial partners to define the design scope for residential and light commercial GSHP and ASHP systems. This will include cooling, heating, and dual use applications of varying cooling capacity. Two VDHX prototypes will be designed, fabricated, and tested for a residential and commercial load, respectively. These prototypes will be tested at our university partners psychrometric facility. Results will be used to design a final, VDHX-based air handler prototype for a residential load. This unit will be used to validate VDHX performance as part of an air handler system for DOE and our partners. Commercial Applications and Other Benefits: The VDHX has direct application to the residential and commercial HVAC market as a highly-efficient indoor heat exchanger that will reduce HVAC power consumption. This, in turn, reduces the carbon footprint of these systems, arrests the rising power demand associated with HVAC, and saves consumers money. In addition, the VDHX provides integral particulate and biological filtration capable of increased indoor air quality compared to conventional heat exchangers. This could allow for tighter ventilation control and a further reduction in power consumption. Finally, the VDHX is highly corrosion resistant and not limited to high thermal conductivity materials. As such, this heat exchanger can be made from easily recyclable, cost effective, and corrosion resistant materials. All of these benefits make the VDHX an attractive heat exchanger for the HVAC market.