Feasibility Analysis and Performance Evaluation and Optimization of a DXSAHP Water Heater Based on the Thermal Capacity of the System: A Case Study

Abstract

The present work conducts an evaluation of the feasibility and the overall performance and consequent optimization of a direct expansion solar assisted heat pump (DXSAHP) employed for domestic water heating. For the study conducted R134a, R404A, R407C and R410A working fluids were evaluated as well as the use of four, six and eight flat-plate solar collectors and a worktime ranging from 1 to 6 h. The case study is based in Mexico City with a 300 L container and a hot water outlet temperature of 51 °C. The paper introduces a new evaluation criterion based on the thermal capacity and all the evaluations conducted throughout this research revolve around this performance metric. The results show that, the system would require at least 4 h of operation to achieve the outlet temperature. Additionally, it was found that the R410A refrigerant has the best heat transfer properties; with an average condensation heat rate of 6.31 kW, followed by the R407C with 5.72 kW, the R404A with 5.42 kW and the R134a with 5.18 kW. Diversely, the R134a refrigerant requires 0.402 kW of compression work, 62% less than the R410A, which requires 1.06 kW. Consequently, R134a delivers the highest COP, which ranges from 7 to 14, followed by the R407C and R404A refrigerants, which present a similar behaviour between them, with COP ranging from 5 to 9 and 4 to 8, respectively, and finally the R410A, achieving the lowest COP, ranging from 3.5 to 6.5. Moreover, it was found that the R134a presents a higher dispersion regarding the energy exchange rate, which reveals that it is the fluid most susceptible to external factors, such as the weather. Contrarily, the remaining refrigerants present a more consistent performance. Finally, the optimization revealed that the R407C refrigerant is the most suitable given that it requires 20% less compression work than the R404A. This provides the heat pump system with a steadier behaviour, a COP ranging from 7 to 8, 30% higher than R410A, a worktime decrease of 1.5 h and heat transfer area of 5.5 flat-plate solar collectors, equivalent to a 31% reduction, both compared to R134a.

Analysis of the Potential of Solar‐Assisted Heat Pumps: Technical, Market, and Social Acceptance Aspects

“…Technoeconomic analysis was also performed to optimize the components’ design and selection and to define the feasibility of these HPs at system level. In De León‐Ruiz et al, [ 45 ] genetic algorithms and artificial neural networks are used for a multiobjective optimization. Parameters used for the optimization include the number of solar collectors and different working fluids.…”

Review on Solar Assisted Heat Pump Water Heating System

“…Kong et al, 2020 [35] practically checked the performance of DX-SAHP system with R290 refrigerant and concludes that the 200L of water gets heat up from 15.3℃ to 54.9℃ and the COP of the system is 2.12-4.43 in the presence of 592 Wm -2 average solar radiation with wind speed of 1.15ms -1 . Lean-Ruiz et al, 2019 [36] practically checked the performance of different refrigerant and resulted that R134a takes 0.402 kW of compressing effort, which is 62% less than R410A, which needs 1.06 kW, As a result, R134a has the greatest COP, ranging from 7 to 14, then by R407C and R404A coolants, which have similar behavior, with COP range from 5 to 9 and 4 to 8, correspondingly, and lastly R410A, which has the lowest COP, range from 3.5 to 6.5. Furthermore, it was discovered that R134a has a greater dispersion in terms of energy exchange rate, indicating that it is the liquid most subject to external conditions such as weather.…”

Energy Performance Analysis of R32 and R134a Refrigerant for Spring Pool Water Heater

“…It also exhibits good performance and safety levels [20]. Additionally, R134a refrigerant boasts a higher Coefficient of Performance (COP) than other refrigerants [21,22].…”