A dynamic performance simulation model of flat-plate solar collectors for a heat pump system

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.

Download Full-text

Multicriteria performance investigations of a hybrid ground source heat pump system integrated with concentrated photovoltaic thermal solar collectors

Energy Conversion and Management ◽

10.1016/j.enconman.2019.111862 ◽

2019 ◽

Vol 197 ◽

pp. 111862 ◽

Cited By ~ 8

Author(s):

Yuzhu Chen ◽

Jiangjiang Wang ◽

Chaofan Ma ◽

Guohua Shi

Keyword(s):

Heat Pump ◽

Ground Source Heat Pump ◽

Solar Collectors ◽

Pump System ◽

Heat Pump System ◽

Ground Source

Download Full-text

Optimization of Working Ground Heat Storage With Seasonal Regeneration

Advanced Energy Systems ◽

10.1115/imece2006-14393 ◽

2006 ◽

Cited By ~ 2

Author(s):

Pawel Olszewski

Keyword(s):

Energy Storage ◽

Heat Exchange ◽

Heat Pump ◽

Input Data ◽

Heat Storage ◽

Target Function ◽

Working Fluid ◽

Solar Collectors ◽

Pump System ◽

Heat Pump System

The aim of the research was an optimization of long-term heat storage with seasonal regeneration. Energy consumption for central heating during wintertime, transfererred from ground energy storage using a heat exchange device, is the operating principle of such systems. Warmed working fluid is then used in a heat pump system. However, more accurate calculations showed that over time of usage, there is a trend toward cooling at deeper round layers. Such a situation leads to a lowering of ground potential when using heat pump systems. A possible solution to this problem is the application of summer regeneration: during summer months, the working fluid is firstly warmed in solar collectors, and then forced into the same boreholes. The numerical model of a vertical, ground heat exchange device (configured as a "pipe in pipe", known as a Fields' pipe) was specially developed. Temperature distribution of the working fluid along the pipe was one of the boundary conditions, for the co-axial, time-variable, heat conduction task, which described the heat flow in energy storage. The numerical simulation of solar collectors work was based on the Hottel - Whillier - Bliss equation, in which energy flow from the solar collector is calculated, dependant on external parameters such as: insulation or ambience temperature. The combination of three computational parts- the ground heat exchange device, energy storage area and solar collectors battery- allows the target function to be defined for task optimization. The subject of optimization was an energy quantity, which can be taken from energy underground storage, and then utilized by the heat pump system. In the summarized paper, a combination of the input data, which influenced the efficiency of energy storage, was chosen. Hypothetical data were: outside diameter and length of heat exchange device, distance between pipes, fluid flow through the pipe during charge and discharge processes or temperature of inlet working fluid. The influence of individual parameters on the target function, holding all input data constant, was analyzed. A developed evolutionary numerical code known as GENOCOP I (GEnetic algorithm for Numerical Optimization for COnstrained Problems) [3] was used for optimization. After preliminary correction of boundary values of the input data, nine attempts of optimization were taken up. The research results identified optimal values of input parameters for which maximum energy could be taken from ground storage.

Download Full-text

The Thermal Performance of Refrigerant Cooled Solar Collectors in a Solar Source Heat Pump System

Transactions of the Canadian Society for Mechanical Engineering ◽

10.1139/tcsme-1984-0007 ◽

1984 ◽

Vol 8 (1) ◽

pp. 40-43

Author(s):

Sui Lin ◽

Kalman I. Krakow

Keyword(s):

Heat Pump ◽

Thermal Performance ◽

Solar Collectors ◽

Pump System ◽

Heat Pump System ◽

Solar Source

Download Full-text

Experimental Analysis of an Air Heat Pump for Heating Service Using a “Hardware-In-The-Loop” System

Energies ◽

10.3390/en13174498 ◽

2020 ◽

Vol 13 (17) ◽

pp. 4498 ◽

Cited By ~ 1

Author(s):

Paolo Conti ◽

Carlo Bartoli ◽

Alessandro Franco ◽

Daniele Testi

Keyword(s):

Heat Pump ◽

Dynamic Performance ◽

Plant Performance ◽

Coefficient Of Performance ◽

Weather Data ◽

Hardware In The Loop ◽

Pump System ◽

Heat Pump System ◽

Experimental Campaign ◽

Experimental Apparatus

Estimating and optimizing the dynamic performance of a heat pump system coupled to a building is a paramount yet complex task, especially under intermittent conditions. This paper presents the “hardware-in-the-loop” experimental campaign of an air-source heat pump serving a typical dwelling in Pisa (Italy). The experimental apparatus uses real pieces of equipment, together with a thermal load emulator controlled by a full energy dynamic simulation of the considered building. Real weather data are continuously collected and used to run the simulation. The experimental campaign was performed from November 2019 to February 2020, measuring the system performances under real climate and load dynamics. With a water set point equal to 40 °C, the average heat pump coefficient of performance was about 3, while the overall building-plant performance was around 2. The deviation between the two performance indexes can be ascribed to the continuous on-off signals given by the zone thermostat due to the oversized capacity of the heat emission system. The overall performance raised to 2.5 thanks to a smoother operation obtained with reduced supply temperature (35 °C) and fan coil speed. The paper demonstrates the relevance of a dynamic analysis of the building-HVAC system and the potential of the “hardware-in-the-loop” approach in assessing actual part-load heat pump performances with respect to the standard stationary methodology.

Download Full-text