Residential Heat Pump Water Heater Research Articles

Transient refrigerant and oil distribution in a residential heat pump water heater system: Experiments and model

• Transient refrigerant and oil retention in a heat pump water heater are measured. • Models are built to predict refrigerant and oil retention in two heat exchangers. • Models are validated against the experimental data. This paper presents an experimental and numerical investigation of the transient refrigerant and oil distribution in a residential heat pump water heater (HPWH) system. In the experiments, R134a is paired with POE 22 oil. The quick closing valve technique (QCVT) is used to trap the refrigerant and oil in each section of the system. The trapped refrigerant mass is measured after recovered by liquid nitrogen. The retained oil mass in each section, except for the compressor, is determined by the mix and sample technique (MST). Five experiments are conducted to cover a full warm-up of five hours. The experimental data shows that most of the refrigerant is in the heat exchangers. During the water warm-up, the inventory of the refrigerant generally decreases in the evaporator, while in the condenser, it decreases in the first three hours and later increases. The measurements also indicate that most of the oil stays in the compressor and the escaped oil is mainly retained in the heat exchangers. Besides, a model is developed to predict the refrigerant and oil retention in the heat exchangers by applying the mixture vapor quality to calculate the void fraction. The developed model predicts the refrigerant inventory in the condenser with an average deviation of 7.4%, and in the evaporator, 9.1%. The average deviations in the predictions of the oil retention in the two heat exchangers are 15.8% and 10.2%.

Increasing the Number of Installed Residential Heat Pump Water Heaters in the USA Through Improved Technology and Utility Programs

Purpose of ReviewHeat pump water heaters (HPWHs) offer an efficient alternative to electric resistance water heaters, but they suffer from limited market penetration. This paper reviews the current state of HPWHs in the USA, focusing on technology developments and programs to increase adoption. What technological improvements are needed to make HPWHs a good fit in more homes? What are the best ways of promoting HPWHs to consumers?Recent FindingsImproved communication and controls will allow HPWHs to provide demand response and follow dynamic utility rates. To enable fuel-switching, HPWHs are being developed that only need a standard 120V outlet. Split HPWHs can alleviate the cooling and noise that limit the use of HPWHs in small homes, multifamily buildings, and cold climates. Additionally, new utility programs aim to train installers and provide incentives to distributors to increase the number of HPWHs installed.SummarySome utilities offer novel incentive programs that have led to increased customer uptake. Those advances, coupled with improved controls for load shifting and new products such as split HPWHs and HPWHs that can run on 120V power, may finally move the market forward.

Evaluation of Effect of Providing Power System Balancing Reserve from Residential Heat Pump Water Heaters

Evaluation of Effect of Providing Power System Balancing Reserve from Residential Heat Pump Water Heaters

R290 (propane) and R600a (isobutane) as natural refrigerants for residential heat pump water heaters

Growing awareness of the potential environmental impacts of various refrigerants has led to the phasedown of hydrofluorocarbon (HFC) refrigerants and to initiatives replacing HFCs with hydrocarbons or other environmentally friendlier fluids. This study evaluated the performance of R290 (propane) and R600a (isobutane) as substitutes for R134a (a HFC) for heat pump water heating (HPWH). A component-based model (calibrated against the experimental data) was used to predict the performance of the HPWH system. Key performance parameters such as unified energy factor, first hour rating, condenser discharge temperature, thermal stratification in the water tank, and total refrigerant charge were investigated. Analysis results suggest that both alternative refrigerants could provide comparable system performance to that of the baseline system containing R134a, with one caveat. As a drop-in alternative, R290 was found to be a better substitute for R134a, whereas R600a is expected to provide similar performance if the compressor size is increased to provide similar heating capacity. Significant reductions in system charge and lower condenser discharge temperatures were identified as additional benefits.

R1234yf and R1234ze(E) as low-GWP refrigerants for residential heat pump water heaters

Owing to the growing concerns about the relatively high global warming potential (GWP) of current refrigerants, a serious effort is in progress to find lower-GWP substitutes. The hydrofluoroolefin (HFO)-based refrigerants R1234yf and R1234ze(E) are being considered for use in multiple heating, ventilation, air conditioning, and refrigeration applications because of their very low GWP. A study was conducted to model a residential heat pump water heater using these HFOs. A system model was calibrated using experimental data and the calibrated model was used to evaluate the potential of HFOs to replace R134a. A series of parametric analyses were used to investigate the impacts of condenser wrap pattern, condenser tube size, evaporator size, and heat loss factor from the storage tank. It has been shown that both R1234yf and R1234ze(E) can be substituted for R134a with comparable performance and no substantial modifications to the original system. This study presents a detailed feasibility analysis for successful replacement of high-GWP refrigerants with low-GWP refrigerants with acceptable performance.

Bomba de calor para calentamiento residencial de agua en Santafé de Bogotá

Here we present a basic development of a residential heat pump water heater for local use. It was designed, built and tested as a replacement for an electric resistance water heater. Results were succesful and proved energy efficiency heat pump water heater's advantage. Based on an experimental design methodology, performance was improved by mean of adjusting parameters to appropriate levels. Also, a market analysis facing the possibilities of heat pump water heater was made realizing the economical capability of local users. Finally, we recomend some key points to direct the local development of this technology.