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Cooling circuits can be improved by using a desuperheater. A series connected desuperheater increases the efficiency of the circuit and allows the waste heat to be used, e.g., for DHW preparation. The study investigates the behavior of a parallel connected desuperheater for DHW preparation in an experimental cooling circuit. The basic parameters of the cooling circuit (efficiency, pressure, temperature and energy consumption) were evaluated when operating 1. with only a condenser and 2. with a condenser and a desuperheater connected in parallel. The results of the study show that a parallel connected condenser and desuperheater reduces the overall efficiency of the cooling circuit. [ABSTRACT FROM AUTHOR]

In order to make the superheated steam flowing at high speed complete the desuperheating process in the pipeline with limited distance, so as to save the production cost, this paper makes structural innovation on the existing equipment, a solution to install static mixing elements in the pipeline downstream of the nozzle of the desuperheater is proposed to improve the performance of the desuperheater without increasing the cost of nozzle atomization. Based on Fluent software, the working process of the new desuperheater is numerically simulated, and its working mechanism and desuperheating effect are visually analyzed. Compared with the traditional desuperheater, the desuperheating range of the new desuperheater in the pipeline with the same distance is increased by about 70.8%, and the temperature non-uniformity coefficient is reduced by about 75.5%. Furthermore, the validity of the above simulation results is verified by experiments.

Thermodynamic (energy and exergy) analysis of steam cooling process in the marine steam propulsion plant is presented in this research. Steam cooling is performed by using Desuperheater which inject water in the superheated steam to obtain wet steam. Wet steam is used in auxiliary heaters for various heating purposes inside the marine steam propulsion system. Auxiliary heaters require wet steam due to safety reasons and for easier steam condensation after heat transfer. Analysis of steam cooling process is performed for a variety of steam system loads. Mass flow rates of cooling water and superheated steam in a properly balanced cooling process should have the same trends at different system loads - deviations from this conclusion is expected only for a notable change in any fluid temperature. Reduction in steam temperature is dependable on the superheated steam temperature (at Desuperheater inlet) because the temperature of wet steam (at Desuperheater outlet) is intended to be almost constant at all steam system loads. Energy losses of steam cooling process for all observed system loads are low and in range between 10-30 kW, while exergy losses are lower in comparison to energy losses (between 5-15 kW) for all loads except three the highest ones. At the highest system loads exergy losses strongly increase and are higher than 20 kW (up to 40 kW). The energy efficiency of a steam cooling process is very high (around 99% or higher), while exergy efficiency is slightly lower than energy efficiency (around 98% or higher) for all loads except the highest ones. At the highest steam system loads, due to a notable increase in cooling water mass flow rate and high temperature reduction, steam cooling process exergy efficiency significantly decreases, but still remains acceptably high (between 95% and 97%). Observation of both energy and exergy losses and efficiencies leads to conclusion that exergy analysis consider notable increase in mass flow rate of cooling water which thermodynamic properties (especially specific exergies) strongly differs in comparison to steam. Such element cannot be seen in the energy analysis of the same system. [ABSTRACT FROM AUTHOR]

This paper presents the mathematical modeling of a liquid-to-water heat pump with scroll compressor, brazed plate heat exchangers, additionally built-in liquid-vapor heat exchanger (LVHX) and a desuperheater for domestic hot water (DHW) production. The refrigerant is the zeotropic mixture R407C and the liquid used in the outdoor loop is a propylene-glycol water mixture. Developed mathematical model is validated on experimental data and used as a tool for the heat pump analysis. Simulation results are obtained for the effect of the degree of superheat at the evaporator outlet, the subcooling degree at the condenser outlet, the effect of using or not the LVHX and the effect of using or not the desuperheater for DHW for typical operating conditions of liquid-to-water heat pumps (EN-14,511-2, 2011) in the cooling and heating modes (low and medium temperature applications). Results show that the effect of the degree of superheat or the decision on the suitability of using or not a LVHX may be different for heat pumps that include or not a desuperheater for DHW. In particular, if DHW is a priority, the use of a LVHX is recommended because it leads to higher COP (or EER) values as well as to higher DHW heating powers. [ABSTRACT FROM AUTHOR]

One of the methods for decreasing the temperature of superheated steam is utilizing desuperheaters which by injecting a fine spray of cooling water and maximizing the evaporation surface, lead to reduce the superheated steam temperature. In this study, a counter-current desuperheater in a thermal desalination unit which is used to reduce the outlet steam temperature of a thermo-compressor is simulated by using the discrete phase model (DPM) and the Eulerian-Lagrangian approach. The effect of different parameters such as the vapor velocity, sprayed droplets size, cooling water mass flow rate, the location, and direction of cooling water injection on desuperheaters performance are considered. The results show that mentioned parameters have considerable influence on the performance of desuperheaters. Numerical results of desuperheater outlet steam temperature show good agreement with experimental data with an average error of 4.89%. [ABSTRACT FROM AUTHOR]

Waste heat from cooling circuits can be a useful source of energy for other applications, such as domestic hot water heaters. Furthermore, by removing waste heat from the cooling circuit, its effectiveness can theoretically be enhanced. A number of previous studies have shown that waste heat can be effectively harvested by installing a desuperheater in the cooling circuit between the condenser and compressor. More recently, studies have concentrated on applying heat pumps in conjunction with desuperheaters in low energy houses. In this study, we describe an experimental laboratory-scale cooling circuit with a serially connected desuperheater for heating domestic hot water. We were able to verify that installation of a desuperheater between the compressor and condenser significantly increased the energy eficiency ratio of the experimental cooling circuit, thereby confirming the hypothesis that simultaneous use of waste heat increases the eficiency of cooling circuits. [ABSTRACT FROM AUTHOR]

Heat pumps with a three-media refrigerant/phase change material (PCM) water heat exchanger (RPW-HEX), integrated in the hot superheated section after the compressor, have a promising potential for electric energy savings. The RPW-HEX operates as a desuperheater that stores the sensible energy provided by the hot gas during heating and cooling operation for later heat transfer to domestic hot water (DHW) storage devices. So far, such a system has not yet been implemented and analysed in an overall system suitable for heating, cooling and DHW generation. In the present work, the operation of a prototypical heat pump with integrated RPW-HEX connected to three artificial apartments, was demonstrated in the laboratory under controlled ambient conditions. For this purpose, two RPW-HEX modules with a total storage capacity of about 5 kWh were integrated into an R32 air-source heat pump with a heating power of about 7.7 kW at − 10 ∘ C ambient temperature and a feed water temperature of 45 ∘ C. Technical feasibility and operation with rule-based control strategies have been successfully demonstrated for realistic use cases. Besides individual tests, the heat pump was operated over 48 hours with and without RPW-HEX at an ambient temperature of − 2 ∘ C, a feed water temperature for the heating system of 40 ∘ C. Both systems, achieved the same average COP, but the system with RPW-HEX was able to provide a 10 K higher average feed water temperature for DHW generation compared to the system without RPW-HEX. For the same feed water temperatures for DHW generation, an enhancement of about 3.1% of the average COP can be expected with the current system. This is about 60% of the theoretically possible value. Furthermore, for a low feed water temperature for heating of about 32 ∘ C at − 2 ∘ C, an enhancement of the average COP up to 9.4% can be expected for the analysed heating and DHW scenario with an improved design. • Integration of a refrigerant/PCM/water heat exchanger as a desuperheater. • First demonstration of the concept with three artificial apartments in the lab. • Experimental comparison with a conventional heat pump system. • Detailed experimental analysis of the critical points of the technology. • Expected enhancement of the average COP up to 10% for the analysed conditions. [ABSTRACT FROM AUTHOR]

Abstract: Various means of producing domestic hot water (DHW) with renewable energy in zero net energy homes (ZNEH) are examined for two climates (Montréal and Los Angeles). Four alternatives are examined: (i) a regular electric hot water tank; (ii) the desuperheater of a ground-source heat pump (GSHP) with electric backup; (iii) thermal solar collectors with electric backup; and (iv) a heat pump water heater (HPWH) indirectly coupled to a space conditioning GSHP. Results show that heating DHW with thermal solar collectors with an electric backup (which is either provided by the photovoltaic (PV) panels or the grid in a ZNEH) is the best solution for a ZNEH. The second part of this paper focuses on determining what should be the respective areas of the thermal solar collectors and PV array to obtain the least expensive solution to achieve total DHW production with renewable energy. [Copyright &y& Elsevier]

In subtropical regions, a desuperheater heat recovery system for service hot-water heating can be applied. However, in colder seasons when building cooling load is reduced, a standard water-cooling tower may be reversibly used to extract free heat from ambient air to make up the reduction of heat source for water heating. Previous related work included developing an analytical method for evaluating the heat and mass transfer characteristics in a reversibly used water-cooling tower (RUWCT), which cannot be used to determine the air and water states at any intermediate horizontal sections along the tower height within an RUWCT.This paper presents a detailed numerical analysis by which the air and water states at any horizontal plane along the tower height within an RUWCT can be determined. The numerical analysis has been partially validated using the experimental data from an installed RUWCT in a hotel building in southern China.The numerical analysis reported in this paper, together with the Analytical Method previously developed, provides a complete method for the analysis of heat and mass transfer characteristics within and at the boundaries of an RUWCT. [Copyright &y& Elsevier]

In sub-tropical regions, a standard water cooling tower may be reversibly used, as part of a desuperheater heat recovery system for service hot water heating, to extract free heat from ambient air in colder seasons when building cooling load is reduced. Part of chilled water is pumped into a RUWCT where it is heated by warmer ambient moist air. This paper presents a simulation study where a steady-state mathematical model for such a desuperheater heat recovery system complete with a RUWCT has been developed. Simulation results based on the specifications of an actual chiller plant have demonstrated that the model developed is stable and behaves as expected.With the model developed, the operating characteristics of the refrigeration system with a desuperheater and a RUWCT were studied. The required flow rate of chilled water to be pumped into the RUWCT was calculated in order to satisfy a certain heat load. The maximum heating capacity of the system under different operating conditions were also evaluated. The simulation results also indicated that the use of a RUWCT would achieve a higher energy efficiency than the use of electrical heating as backup heat provisions when building space cooling load is reduced. [Copyright &y& Elsevier]