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information). It could also potentially provide a service technician with operational maintenance data in advance of system failures. Advanced Heat Exchangers. The performance of heat exchangers used in residential and commercial heating and cooling systems is well below what is currently technologically possible. Improvements to the air to refrigerant heat exchanger can increase the heat exchanger heat transfer coefficient (HTC) leading to improvements to both operating efficiency and broader operating temperature ranges (Chapp 1998). One such example are micro-channel heat exchangers, which until recently were only common in automotive radiators but are now beginning to appear in some mini-split and VRF systems. Mass production of advanced heat exchangers will enable an iASHP to heat reliably when it is cold outside without backup heating and/or provide better cooling or moisture extraction when it is hot outside. Potential energy savings of 0.7 to 1.1 quads is possible by the increasing the condensing unit’s heat transfer coefficient in U.S. market heat pumps (Westphalen 2006). Work currently funded by the US DOE Office of Energy Efficiency and Renewable Energy seeks to use advanced heat exchangers to reduce the amount of refrigerant, and material needed while increasing performance by 20% (US DOE 2016) New Refrigerants. The phase-out of HFC refrigerants will likely result in a switch to hydroflouroolefins (HFOs) or HFO/HFC blends, hydrocarbons (HCs), or other “natural” refrigerants like CO2 or ammonia. This transition will not be easy, but if integrated well can result in better performance, safety, and enhanced utility grid resiliency. HFC refrigerants such as diflouroethane (R32) and hydrocarbons such as isobutane (R600) or propane (R290) offer lower cost and often improved performance, but present challenges because of their flammability. R32 is slightly flammable (an A2 refrigerant) though it is extensively used now in mini-split systems throughout Asia. Another likely replacement is R744 (CO2), which offers produces higher COP values under large changes in temperature with enabling it to operate cold climates while delivering very high temperature (190 F) output temperatures. Hydronic Systems and Thermal Storage. The combination of new refrigerants coupled with hydronic systems could improve seasonal COP by 10-12% over current R410a systems (Konghuayrob , 2016). While current hydronic systems are often more expensive to install, future standards of practice may eliminate this as added cost is not intrinsic to hydronic versus refrigerant systems. In addition to improved performance, are four additional benefits of moving to hydronic systems. 1-6 ©2018 ACEEE Summer Study on Energy Efficiency in Buildings 1. 2. 3. The trades needed to install hydronic HVAC equipment do not need a refrigeration certification. The outdoor iASHP unit can be a packaged assembly that provides hot and chilled water, with only hydronic, control wiring, and power connections. The system becomes far more independent of the interior conditions and a system can be placed in defrost mode without delivering cold air to the indoors. In addition, the higher heat capacity of water and energy stored in the system can enable very rapid defrost cycles, reducing loss of capacity impacts in cold ambient conditions. A single system can be tasked with both domestic water heating and hot and chilled water for space conditioning, thus potentially lowering overall system cost.PDF Image | Lync Diagram
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CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
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