Performances of a New Air-to-Water Heat Pump System with Controlled Capacity (original) (raw)
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The impact of the work under partial load on the energy efficiency of an air-to-water heat pump
E3S Web of Conferences
The energy efficiency of air-to-water heat pumps used for central heating depends significantly on the correctness of the device choice. Under given climate conditions, the temperature of the bivalent point defines the amount of energy supplied from an additional source, usually an electric heater, in periods when the power of the heat pump is too low. Commonly overlooked fact is that excess capacity is also unfavourable and has significant, negative impact on the energy efficiency of such a system. In the article, basing on the measurement data of the real installation of the air-to-water heat pump, a significant decrease in the energy efficiency of the device during periods of low energy demand was shown. The average monthly value of SCOP in the warm months was similar or even lower than in the winter months. The reason of this is the operation of the device under partial load. Although the values of COP were very high in short periods of operation, frequent switching on and off of the heat pump reduced its energy efficiency. Also, the length of operation in stand-by mode, i.e. the length of the periods between successive heating cycles, had negative influence on energy efficiency.
Air-to-water heat pump assessment: Part 1 – Experimental setup
E3S Web of Conferences, 2021
This paper is part 1 of the investigation on the exergetic and exergoeconomic parameters of an existing system with an air-to-water heat pump unit as a heat source. Part 1 presents the used experimental setup. The main aim of the conducted experimental tests is to develop a model of produced heat transfer rate and energetic COP at different ambient conditions. The obtained data is used in Part 2 of the study where the exergetic and exergoeconomic assessment is carried out. The performance of the considered system is evaluated using Seasonal Exergy Efficiency. Moreover, Part 2 of the study has presented the formulation of the cost of the product, and cost allocation within the heat pump unit based on exergy.
Journal of Energy in Southern Africa, 2021
Air source heat pump (ASHP) water heaters are efficient devices for sanitary hot water heating. The coefficient of performance (COP) of the air to water heat pump (AWHP) is constantly lower than that of the corresponding ASHP unit. The study focused on determining the COP of both the ASHP unit and the AWHP. This was achieved by the implementation of both experimental and simulation methods, with the help of a data acquisition system and the REFPROP software. The system comprised of a 1.2 kW split type ASHP unit and a 150 L high pressure geyser. A power meter, flow meters, temperature sensors, pressure sensors, ambient temperature and relative humidity sensor were installed at precise locations on the split type AWHP. Controlled volumes of 150, 50 and 100 L were drawn off from the AWHP during the morning, afternoon and evening for a year. The average COP for the summer and winter, in terms of the input electrical and output thermal energies of the AWHP were 3.02 and 2.30. The COPs of...
International Journal of Automotive and Mechanical Engineering, 2013
This paper presents an experimental energetic and exergetic comparison for a heat pump system that can be run in different modes as air to air and air to water. Components of the heat pump do not change when the running mode changes, except for the condenser. This means that some external and internal effects (like compressor type, pipe lines) that can affect the system performance will be the same for each running mode. The comparison which was made in this study demonstrates which system leads to an efficient conversion and supply of energy and exergy. In the analysis, four balance (mass, energy, entropy and exergy) equations are applied to the system for the two modes. Exergy and energy efficiency values for both systems are given, while exergy destructions in each of the systems are determined and presented. It is seen that the heat pump unit which has the highest COP value is the air to air type (3.45-3.8); second is the air to water type (3.35-3.41). The exergy efficiency of t...
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WSEAS Transactions on Heat and Mass Transfer
The heat pumps are alternative heating/cooling systems more energy efficiency and unless pollutant in comparison with classical systems (liquid or gas fuel boiler). A large number of heat pump systems have been used in residential and commercial buildings throughout the world due to the attractive advantages of high energy and environmental performances. This paper presents the economic, energy and environmental performance criteria which show the opportunity to implement a heat pump in a heating/cooling system. A computational model of annual energy consumption for an air-to-water heat pump based on the degreeday method and the bin method implemented in a computer program is developed. In addition, from a case study a comparative economical analysis of heating solutions for a building is performed and the energy and economic advantages of building heating solution with a water-to-water heat pump are reported. Finally, the renewable energy sources contribution from heat pump sales ...
Energy performance of air-to-water and water-to-water heat pumps in hotel applications
Energy Conversion and Management, 2003
We present work on measurement of the energy performance of heat pumps for hotel operations in subtropical climates. Two city hotels in Hong Kong were investigated. The first case was an application of an air-to-water heat pump to provide heating for an outdoor swimming pool during the heating season. The second case was the installation of three water-to-water heat pumps to complement an existing boiler system for hot water supply. The heating energy output and corresponding electricity use were measured. The heat pump energy efficiency was evaluated in terms of the coefficient of performance (COP), defined as the heating energy output to the electrical energy use. The air-to-water heat pump provided 49.1 MW h heating while consuming 24.6 MW h electricity during the 6 1 2-month heating season from mid-October to April. For the water-to-water heat pumps, the estimated annual heating output and the electricity use were 952 and 544 MW h, respectively. It was found that the heat pumps generally operated in a COP range of 1.5-2.4, and the payback period was about two years, which was considered financially attractive.
Energy, 2013
In this study, we designed a multifunctional heat pump system using just one scroll compressor and which can be run in four different modes, namely air to air, air to water, water to water and water to air, in order to make an experimental energetic and exergetic performance comparison. Experimental system consists of two condensers and two evaporators and uses R22 as working fluid. One of the evaporators and condensers uses water and the others use air as heat source/sink. Heating capacities of four heat pump types are equal to each other. It is realized by adjusting the mass flow rate and temperature level of external fluid of condenser. Results show that the heat pump unit which has the maximum COP (coefficient of performance) value is water to air type with 3.94 and followed by water to water type with 3.73, air to air type with 3.54 and air to water type with 3.40. Ranking of four heat pump types with respect to their mean exergy efficiency is as follows; water to air type with 30.23%, air to air type with 30.22%, air to water type with 24.77% and water to water type with 24.01%. Exergy destruction rates of the systems were investigated in this study and the results revealed that the heat pump type which has the maximum exergy destruction is air to air type with 2.93 kW. The second highest one is air to water type with 2.84 kW. The third highest one is water to air type with 2.64 kW and last one is water to water type with 2.55 kW. It is understood that the temperature of the evaporator external fluid affects the exergetic efficiency of the system more than the mass flow rate. In contrast to the previous, the dominant parameter which has more important effect on the exergy destruction of the heat pump unit is the mass flow rate of evaporator external fluid.
Performance Analysis of a Combined Heat Pump
2016
Abstract. During the past few decades, all Gulf States have experienced a rapid growth in living standard, which was naturally associated with rapid increase in demand for electricity and potable water. Due to changes of living style, large portion of the electric power was consumed for air conditioning (A/C). Lack of natural water resources and striving needs for water made desalination the main technology to provide potable water. In an effort to search for a novel method for producing fresh water, the present paper investigates a combination of a heat pump (HP) with a dehumidification process to extract water from the atmospheric air. The unit supplies 1.586 m3/s air to an office building (250 m2 area) by the sea side in Jeddah, Kingdom of Saudi Arabia (KSA) where the average ambient temperature is 34oC and relative humidity of 71%. The unit has two series evaporator-coils to maximize the water condensation process by reducing the air exit temperature to 8 oC. The performance of ...
New Methodology of Characterization of Seasonal Performance Factor of An Air-To-Water Heat Pump
2010
The threat of the global warming is alarming. The increase in oil prices remains a persistent worry and today's energy challenges are truly critical. In this context, heat pumps in the residential sector appear to be an interesting solution to reduce energy consumption and emissions of greenhouse gases. The French government has developed, under the leadership of the "Grenelle of the environment", two successive tax incentives that have increased the number of heat pumps (HP) sold in France for heating and / or production of domestic hot water. European standards used to characterize the air-to-water heat pump performances are based on one test at maximum load operation for an outdoor temperature of 7°C and an outlet temperature of hot water of 35°C. These operating conditions are very different from real life conditions. They can even be quite unrealistic as they exclude start-up and shutdown, defrosting of the outdoor unit, the part load impact, and the weather and water temperature lifts. In this paper, an experimental study is performed on three air-to-water heat pumps. Tests are realized for outdoor temperature varying between-10°C and 14°C and for three water temperature levels. These tests allowed calculating the average heating seasonal performance factor of the HPs. The aim of the experimental study is to select a limited number of testing conditions and to establish a methodology to assess, more realistically the HP performance.