Conventional air-source heat pumps (ASHPs) experience rather poor performance in cold climate areas. The heating capacity and efficiency of conventional ASHPs decrease significantly as the outdoor temperature decreases. The major R D challenges are to limit this ASHP heating capacity and efficiency degradation at low and extremely low ambient temperatures. Vapor injection (VI) compressors are able to provide better efficiency and larger capacity at low ambient temperatures. A prototype air-source cold climate heat pump (CCHP), using tandem vapor injection (VI) compressors and inter-stage flash tank, was developed. The CCHP has two identical VI compressors in parallel, which works with a two-stage indoor blower and two-stage thermostat. At moderately low ambient temperatures, only one compressor is called, and at extremely low ambient temperatures, both the compressors are used. The prototype was installed in Fairbanks, Alaska and underwent field testing for six months. The CCHP successfully operated down to −30 °F (−35 °C) and was able to meet the building heating load with good efficiency in a wide range of ambient temperatures. At −30 °F (−35 °C), the CCHP delivered 75

A preliminary evaluation of the performance of a consumer-based control system was conducted by the Oak Ridge National Laboratory (ORNL) and Southwest Gas as part of a cooperative research and development agreement (CADA) authorized by the Department of Energy (DOE) (Manderekal et al. 2013). The goal of the research was to evaluate the low-cost approach as a solution for implementing a supervisory control system for a residential gas-operated heat pump. The design incorporated two consumer-based Microcon-trollers; the Arduino IVega-2650 and the BeagleBone (white). Tenliveton (17.6 kft) heatpump systems were designed, fabricated, and operationally tested in the Las Vegas, NV region. A robust-data set was produced that allowed detailed assessment ofthe reliability and the operational performance of the newly developed control system. Experiences gained from the test provided important points of improvement for subsequent evolution of the heat pump technology.

In response to environmental concerns raised by the use of refrigerants with high Global Warming Potential (GWP), the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) has launched an industry-wide cooperative research program, referred to as the Low-GWP Alternative Refrigerants Evaluation Program (AREP), to identify and evaluate promising alternative refrigerants for major product categories. After successfully completing the first phase of the program in December 2013, AHRI launched a second phase of the Low-GWP AREP in 2014 to continue research in areas that were not previously addressed, including refrigerants in high ambient conditions, refrigerants in applications not tested in the first phase, and new refrigerants identified since testing for the program began. Although the Ozone Depletion Potential of R-410A is zero, this refrigerant is under scrutiny due to its high GWP. Several candidate alternative refrigerants have already demonstrated low global warming potential. Performance of these low-GWP alternative refrigerants is being evaluated for Air conditioning and heat pump applications to ensure acceptable system capacity and efficiency. This paper reports the results of a series of compressor calorimeter tests conducted for the second phase of the AREP to evaluate the performance of R-410A alternative refrigerants in a reciprocating compressor designed for air conditioning systems. It compares performance of alternative refrigerants ARM-71A, L41-1, DR-5A, D2Y-60, and R-32 to that of R-410A over a wide range of operating conditions. The tests showed that, in general, cooling capacities were slightly lower (except for the R-32), but energy efficiency ratios (EER) of the alternative refrigerants were comparable to that of R-410A.

This work considers the possibilities of an air-based Brayton cycle to provide the power, heating and cooling needs of fast-food restaurants. A model of the cycle based on conventional turbomachinery loss coefficients is formulated. The heating, cooling and power capabilities of the cycle are extracted from simulation results. Power and thermal loads for restaurants in Knoxville, TN and in International Falls, MN, are considered. It is found that the cycle can meet the loads by setting speed and mass flow-rate apportionment between the power and cooling functional sections. The associated energy costs appear elevated when compared to the cost of operating individual components or a more conventional, absorption-based CHP system. A first-order estimate of capital investments is provided. Suggestions for future work whereby the operational costs could be reduced are given in the conclusions. (C) 2016 Elsevier Ltd. All rights reserved.

While there have been extensive studies on thermofluid characteristics of different magnetocaloric refrigeration systems, a conclusive optimization study using non dimensional parameters which can be applied to a generic system has not been reported yet. In this study, a numerical model has been developed for optimization of active magnetic refrigerator (AMR). This model is computationally efficient and robust, making it appropriate for running the thousands of simulations required for parametric study and optimization. The governing equations have been non-dimensionalized and numerically, solved using finite difference method. A parametric study on a wide range of non-dimensional numbers has been performed. While the goal of AMR systems is to improve the performance of competitive parameters including COP, cooling capacity and temperature span, new parameters called "AMR performance index-1" have been introduced in order to perform multi objective optimization and simultaneously exploit all these parameters. The multi-objective optimization is carried out for a wide range of the non-dimensional parameters. The results of this study will provide general guidelines for designing high performance AMR systems.

The aim of this project was to design a residential fuel fired heat pump and further improve efficiency in collaboration with an industry partner – Southwest Gas, the developer of the Nextaire commercial rooftop fuel-fired heat pump. Work started in late 2010. After extensive search for suitable engines, one manufactured by Marathon was selected. Several prototypes were designed and built over the following four years. Design changes were focused on lowering the cost of components and the cost of manufacturing. The design evolved to a final one that yielded the lowest cost. The final design also incorporates noise and vibration reduction measures that were verified to be effective through a customer survey. ETL certification is currently (as of November 2015) underway. Southwest Gas is currently in talks with GTI to reach an agreement through which GTI will assess the commercial viability and potential of the heat pump. Southwest Gas is searching for investors to manufacture the heat pump and introduce it to the market.

HVAC and water healing equipment consume rip to 47% of the total energy consumption in U.S. households. Electric heating and cooling are important contributors to peak electricity demand and water heating also plays a large role in energy expenditures. The development of a residential fual fired multifunction heat pump that achieves high source energy efficiency for space conditioning and water heating would reduce overall primary energy use for space heating, space cooling, and water heating. The proposed technology (cooling source COP of 1.3, heating source COP of 1.4 and over 30% primary energy usage reduction) results in a significant increase in efficiency compared to present HVAC and water heating equipment. A prototype Fuel Fired Multi-Function Heat Pump (FFMHP) unit is being tested in our laboratory. In the space heating mode, we use a suction line heat exchanger to Ironer the engine heat. In the space cooling mode, an utilize the recovered engine heat to heat water. The FFMHP is modeled using a component-based modeling approach. We have parametric runs to show the performance trends with varying multiple operation parameters.

Based on a detailed steady-state system and component modeling, a rooftop unit system design was developed that is can achieve an integrated energy efficiency rating higher than 20. Fin-and-tube and microchannel heat exchangers were modeled using a segment-to-segment approach, and an AHRI 10-coefficient compressor map used to simulate compressor performance. The system modeling is based on a component-based modeling approach, which facilitates flexible simulation of complicated system configurations. Starting with a baseline system having integrated energy efficiency rating of 16.6, numerous technical options were extensively investigated, i.e., varying compressor sizes, heat exchanger fin densities, fin-and-tube or microchannel heat exchanger, suction line heat exchanger, desiccant wheel, tandem compressor (TD), variable-speed compressor (VS), and condenser evaporative pre-cooling; an innovative system configuration was developed by combining a tandem compression system with a variable-speed compression system. The combined system can achieve a high integrated energy efficiency ratio as well as process the outdoor ventilation air over an extensive range. The design concept for a 20-ton (70.4-kW) unit, as well as a 10-ton (35.2-kW) unit was successfully evaluated. All selected components are readily accessible on the market, and performance predictions were validated against existing rooftop unit products at the rating condition. This article illustrates a potentially cost-effective high integrated energy efficiency ratio rooftop unit design. In addtion, extensive building energy simulations were conducted using EnergyPlus to predict seasonal energy saving potentials and peak power reductions using the high integrated energy efficiency ratio rooftop unit in 16U.S. cities in comparison to a rooftop unit with a minimum efficiency.

To improve the system performance of a gas engine driven heat pump system, an analytical modeling and experimental study has been made by using a desiccant system in cooling operation (particularly in high-humidity operations) and suction line waste heat recovery to augment heating capacity and efficiency. The overall performance of a gas engine driven heat pump system has been simulated with a detailed vapor compression heat pump system design model. The modeling includes (1) a gas engine driven heat pump cycle without any performance improvements (suction liquid heat exchange and heat recovery) as a baseline (both in cooling and heating mode), (2) a gas engine driven heat pump cycle in cooling mode with a desiccant system regenerated by waste heat from the engine incorporated, and (3) a gas engine driven heat pump cycle in heating mode with heat recovery (recovered heat from engine). According to the system modeling results, by using the desiccant system, the sensible heat ratio can be lowered to 40%. The waste heat of the gas engine can boost the space heating efficiency by 25% at rated operating conditions. In addtion, using EnergyPlus, building energy simulations have been conducted to assess annual energy consumptions of the gas engine driven heat pump in 16 U.S. cities, and the performances are compared to a baseline unit that has a electrically driven air conditioner with the seasonal coefficient of performance of 4.1 for space cooling and a gas furnace with 90% fuel efficiency for space heating.

This paper presents a review of the next generation not-in-kind technologies to replace conventional vapor compression refrigeration technology for household applications. Such technologies are sought to provide energy savings or other environmental benefits for space conditioning, water heating and refrigeration for domestic use. These alternative technologies include: thermoacoustic refrigeration, thermoelectric refrigeration, thermotunneling, magnetic refrigeration, Stirling cycle refrigeration, pulse tube refrigeration, Malone cycle refrigeration, absorption refrigeration, adsorption refrigeration, and compressor driven metal hydride heat pumps. Furthermore, heat pump water heating and integrated heat pump systems are also discussed due to their significant energy saving potential for water heating and space conditioning in households. The paper provides a snapshot of the future R&D needs for each of the technologies along with the associated barriers. Both thermoelectric and magnetic technologies look relatively attractive due to recent developments in the materials and prototypes being manufactured.

Lithium Bromide (LiBr) strong solution entering the absorber tends to crystallise when the absorber temperature is increased for a fixed evaporating pressure. This is considered the key technical barrier for the development of a LiBr absorption heat pump water heater. There are several approaches to avoid the crystallisation problem, such as chemical crystallisation inhibitors, heat and mass transfer enhancement and thermodynamic cycle modification. This paper investigates and compares two flow configurations of LiBr absorption heat pump water heater to evaluate the allowable operating conditions for each. The simulation results indicated that introducing the process water through the absorber first results in lower absorber temperature and hence less tendency for crystallisation.