scholarly journals Optimization of absorption systems: case of the refrigerators and heat pumps

2019 ◽  
Vol Volume 30 - 2019 - MADEV... ◽  
Author(s):  
René Tchinda ◽  
Paiguy Armand Ngouateu Wouagfack
Keyword(s):  
Performance Optimization ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Entropy Generation Rate ◽  
Design Parameters ◽  
Working Fluid ◽  
Ecological Design ◽  
Ecological Performance ◽  
Heating Load ◽  
Main Components

The new thermo-ecological performance optimization of absorption is investigated by taking the ecological coefficient of performance ECOP as an objective function. ECOP has been expressed in terms of the temperatures of the working fluid in the main components of the system. The maximum of ECOP and the corresponding optimal temperatures of the working fluid and other optimal performance design parameters such as coefficient of performance, specific cooling load of absorption refrigerators, specific heating load of absorption heat pumps, specific entropy generation rate and the distributions of the heat exchanger areas have been derived analytically. The obtained results may provide a general theoretical tool for the ecological design of absorption refrigerators and heat pumps.

scholarly journals High-temperature heat pump simulator (heatpack) for application in computer laboratory sessions for engineering students

2021 ◽  
Vol 11 (1) ◽  
pp. 16
Author(s):  
Adrián Mota Babiloni ◽  
Carlos Mateu-Royo ◽  
Joaquín Navarro-Esbrí ◽  
Ángel Barragán-Cervera
Keyword(s):  
High Temperature ◽  
Engineering Students ◽  
Waste Heat ◽  
Energy Performance ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Industrial Processes ◽  
Design Parameters ◽  
Working Fluid ◽  
Temperature Heat

A significant amount of energy in the form of heat is lost in industrial processes once it is used in specific processes. Among different technologies, high-temperature heat pumps (HTHP) are a valuable method of recovering low-temperature waste heat in the industry in a very efficient way that can be activated using clean electricity. As a recently investigated technology, they are not yet spread in industrial processes, where traditional technologies are preferred. Therefore, this work shows an HTHP computer program (named HeatPack) to be used as a simulator by the university or technical students of courses included in the area of applied thermodynamics engineering. This interactive and user-friendly platform allows the modification of different operating and design parameters and the working fluid. As outputs, the program provides the rest of the operating parameters and the energy performance of the cycle (quantified by the coefficient of performance, COP). A comparison between the proposed HTHP and a gas boiler is also performed by the program and the energetic, environmental, and economic savings are displayed. Students, as the main target of users of the program, can observe how this technology can provide very relevant emission reductions in comparison with fossil fuel-based boilers, under which situation the energy performance of the HTHP is higher, and which alternative low global warming potential (GWP) refrigerants can provide more advantages. In addition to the educational use, this software can be used to design and study the integration of HTHPs in existing industrial needs to evaluate the feasibility.

scholarly journals Performance Optimization of an Air-Standard Irreversible Dual-Atkinson Cycle Engine Based on the Ecological Coefficient of Performance Criterion

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Guven Gonca ◽  
Bahri Sahin
Keyword(s):  
Performance Optimization ◽  
Pressure Ratio ◽  
Performance Criterion ◽  
Coefficient Of Performance ◽  
Cycle Performance ◽  
Temperature Ratio ◽  
Finite Rate ◽  
Ecological Performance ◽  
Atkinson Cycle ◽  
Internal Irreversibility

This paper presents an ecological performance analysis and optimization for an air-standard irreversible Dual-Atkinson cycle (DAC) based on the ecological coefficient of performance (ECOP) criterion which includes internal irreversibilities, heat leak, and finite-rate of heat transfer. A comprehensive numerical analysis has been realized so as to investigate the global and optimal performances of the cycle. The results obtained based on the ECOP criterion are compared with a different ecological function which is named as the ecologic objective-function and with the maximum power output conditions. The results have been attained introducing the compression ratio, cut-off ratio, pressure ratio, Atkinson cycle ratio, source temperature ratio, and internal irreversibility parameter. The change of cycle performance with respect to these parameters is investigated and graphically presented.

scholarly journals Influence of desorption temperature on the thermodynamic performance of adsorption heat pump

2018 ◽  
Vol 70 ◽  
pp. 01022
Author(s):  
Katarzyna Zwarycz-Makles
Keyword(s):  
Heat Pump ◽  
Heat Pumps ◽  
Adsorption Heat ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Thermodynamic Efficiency ◽  
Efficiency Coefficient ◽  
Desorption Temperature ◽  
Adsorption Heat Pump ◽  
Thermodynamic Performance

In the paper an analysis of the desorption temperature effect on the thermodynamic efficiency of the adsorption heat pumps is presented. The thermodynamic performance of heat pump is determined by Coefficient of Performance (COP) as well as exergetic efficiency coefficient (ηex) at the adsorption equilibrium conditions and compared to the performance at heat of evaporation of the working fluid conditions. Possible estimation of reduced efficiency of adsorption silica gel/water heat pump, as distinct from the equilibrium efficiency in realistic technical system is presented.

Development of a Passive Cooling Panel for Residential Buildings, Integrated Into a Novel “Magnetic/PCM” Ground Coupled Flat Heat Pipe

2008 ◽  
Author(s):  
Gustavo Gutierrez ◽  
Josean Aponte
Keyword(s):  
Heat Pipe ◽  
Residential Buildings ◽  
Low Cost ◽  
Heat Pumps ◽  
Design Parameters ◽  
Working Fluid ◽  
Passive Cooling ◽  
Ground Source Heat Pumps ◽  
Reluctance Motor ◽  
Flat Heat Pipe

New perspectives for reducing heat and electricity consumption in building are emerging with innovative techniques such as highly insulating glazing and super insulated structures, utilization of solar energy, solar cells, hybrid ventilation solutions, energy efficient and demand-controlled ventilation, as well as integration of solutions, energy production in building. A relatively new innovation is the use of ground-source heat pumps that have become popular for both residential and commercial heating and cooling applications because of their higher energy efficiency compared to conventional systems. In this study, a flat heat pipe is proposed for using the enormous heat capacity of the soil as a heat sink to remove heat from the ambient, integrated the principal idea of a linear reluctance motor for the recirculation of the working fluid. Linear oscillating motors have a long history as rotary motors; but the complexity in the design and difficulties on their control limited the use of them. The motor consists of an iron bar, moving inside a coil. During the path of the iron bar an incremental force appears opposing the movement of the bar. For that reason, it is important to control the system and take advantage of that behavior. Reluctance motors can have high power density at a low cost, making them ideal for many applications. In this study, an implementation of the reluctance motor is proposed for using in a recirculation process of a passive cooling panel for residential buildings. Parametric studies are carried out to optimize the design parameters.

Cooling and heating rate limits of a reversed reciprocating ericsson cycle at steady state

2000 ◽  
Vol 214 (1) ◽  
pp. 75-85 ◽  
Author(s):  
D A Blank ◽  
C Wu
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Heat Pump ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Design Parameters ◽  
Optimized Design ◽  
Cooling Mode ◽  
Working Fluids ◽  
Heating And Cooling

The optimal cooling and heating rates for the reversed reciprocating Ericsson cycle with ideal regeneration are determined for heat pump operations. These limiting rates are based on the upper and lower thermal reservoir temperature bounds and are obtained using time and entropy minimization procedures from irreversible thermodynamics. Use is made of time symmetry (a second law constraint) to minimize cycle time. This optimally allocates the thermal capacitances of the cycle and minimizes internal cycle entropy generation. Although primarily a theoretical work, a very practical and extensive parametric study using several environmentally friendly working fluids (neon, nitrogen and helium) is included. This study evaluates the relative contributions of various system parameters to rate-optimized design. The coefficient of performance (COP), and thus the quantity of cooling or heating for a given energy input, is the traditional focus; instead this work aims at the rate of cooling or heating in heat pumps under steady state conditions and using ideal gases as their working substances. The results obtained provide additional criteria for use in the study, design and performance evaluation of employing Ericsson cycles in refrigeration, air conditioning and heat pump applications. They give direct insight into what is required in designing a reversed Ericsson heat pump to achieve maximum heating and cooling rates. The choices of working fluids and pressure ratios were found to be very significant design parameters, together with selection of regenerator and source—sink heat transfer parameters. The parameter most influencing both the heating and cooling mode COPs and the heat transfer rates was found to be the heat conductance of the thermal sink.

Model of irreversible finite-heat capacity heat reservoir absorption heat transformer cycle and its application

2007 ◽  
Vol 221 (12) ◽  
pp. 1643-1651 ◽  
Author(s):  
L Chen ◽  
X Qin ◽  
F Sun
Keyword(s):  
Performance Characteristic ◽  
Variable Temperature ◽  
Coefficient Of Performance ◽  
Cycle Performance ◽  
Working Fluid ◽  
Cycle Model ◽  
Heating Load ◽  
Internal Irreversibility ◽  
General Relations ◽  
Heat Transformer

An irreversible four-temperature-level absorption heat transformer cycle model with variable-temperature heat reservoirs is established, which considers the heat resistances between the heat reservoirs and the working fluid, the internal irreversibility due to internal dissipation of the working fluid, and the heat leakages between the heat reservoirs and the surrounding. The general relations between the heating load and the coefficient of performance are derived, and the general performance characteristic and the optimal performance characteristic are obtained using numerical examples. Moreover, the cycle model and the derived general relations are confirmed by comparing the prediction results of the model and engineering analysis results for real absorption heat transformer, and the cycle performance characteristic are discussed. The results obtained herein can provide some guidance for the optimal design of absorption heat transformer.

Development of a µ-Scale Turbine Expander for Energy Recovery

2009 ◽  
Author(s):  
Marcus Keding ◽  
Piotr Dudzinski ◽  
Martin Tajmar ◽  
Reinhard Willinger ◽  
Klaus Ka¨fer
Keyword(s):  
Heat Pump ◽  
Pressure Difference ◽  
Energy Recovery ◽  
Low Pressure ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Low Flow ◽  
Working Fluid ◽  
Small Scale ◽  
Work Recovery

Waste heat is a primary source of energy loss in many applications. A number of developments around a micro rocket engine at the Austrian Research Centers (ARC) promise innovative energy recovery and micro power generation solutions. Here we focus on the investigation of micro technologies for application in HVAC (heating, ventilating, and air conditioning) systems. The use of μ-scale turbine expanders for work recovery in transcritical CO2 heat pump processes has been identified as most interesting and promising for the application in HVAC cases. One of the main drawbacks of transcritical CO2 heat pumps is the lower COP (coefficient of performance) compared to conventional heat pump systems which originates from the non isothermal heat rejection in the gas cooler. This drawback can be compensated by utilizing the pressure difference between the high pressure and low pressure part of the heat pump for work recovery. This is feasible as the pressure difference is considerably larger in case of CO2 heat pumps compared to conventional systems. Work recovery can be realized by substituting the expansion valve between the high and low pressure side by an expansion machine. Due to the low flow rate of the working fluid, the turbine type is based on the Pelton turbine with specific two phase flow turbine blades. In addition to the turbine part a magnetic coupling, miniature bearings and a small scale generator are important parts of the system. Thermodynamic simulations showed an absolute microturbine power yield between 60 W and 150 W for a 2 kW heating system.

scholarly journals Energy and Exergy Analysis of the Air Source Transcritical CO2 Heat Pump Water Heater Using CO2-Based Mixture as Working Fluid

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4470
Author(s):  
Yikai Wang ◽  
Yifan He ◽  
Yulong Song ◽  
Xiang Yin ◽  
Feng Cao ◽  
...  
Keyword(s):  
Exergy Analysis ◽  
Heat Pumps ◽  
Exergy Efficiency ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Domestic Hot Water ◽  
Practical Applications ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis

Given the large demand nowadays for domestic hot water, and its impact on modern building energy consumption, air source transcritical CO2 heat pumps have been extensively adopted for hot water production. Since their system efficiency is limited by significant irreversibility, a CO2-based mixture could offer a promising drop-in technology to overcome this deficiency without increasing system complexity. Although many CO2 blends have been studied in previously published literature, little has been presented about the CO2/R32 mixture. Therefore, a proposed mixture for use in transcritical CO2 heat pumps was analyzed using energy and exergy analysis. Results showed that the coefficient of performance and exergy efficiency variation displayed an “M” shape trend, and the optimal CO2/R32 mixture concentration was determined as 0.9/0.1 with regard to flammability and efficiency. The irreversibility of the throttling valve was reduced from 0.031 to 0.009 kW⋅kW−1 and the total irreversibility reduction was more notable with ambient temperature variation. A case study was also conducted to examine domestic hot water demand during the year. Pure CO2 and the proposed CO2 blend were compared with regard to annual performance factor and annual exergy efficiency, and the findings could provide guidance for practical applications in the future.

scholarly journals Parametric Investigation of a Ground Source CO2 Heat Pump for Space Heating

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3563
Author(s):  
Evangelos Bellos ◽  
Christos Tzivanidis
Keyword(s):  
Heat Exchanger ◽  
Heat Pump ◽  
Heat Pumps ◽  
Geothermal Field ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Space Heating ◽  
Geothermal System ◽  
Parametric Investigation ◽  
Ground Source

The objective of the present study is the parametric investigation of a ground source heat pump for space heating purposes with boreholes. The working fluid in the heat pump is CO2, and the geothermal field includes boreholes with vertical heat exchangers (U-tube). This study is conducted with a developed model in Engineering Equation Solver which is validated with data from the literature. Ten different parameters are investigated and more specifically five parameters about the heat pump cycle and five parameters for the geothermal unit. The heat pump’s examined parameters are the high pressure, the heat exchanger effectiveness, the temperature level in the heater outlet, the flow rate of the geothermal fluid in the evaporator and the heat exchanger thermal transmittance in the evaporator. The other examined parameters about the geothermal unit are the ground mean temperature, the grout thermal conductivity, the inner diameter of the U-tube, the number of the boreholes and the length of every borehole. In the nominal design, it is found that the system’s coefficient of performance is 4.175, the heating production is 10 kW, the electricity consumption is 2.625 kW, and the heat input from the geothermal field is 10.23 kW. The overall resistance of the borehole per length is 0.08211 mK/W, while there are 4 boreholes with borehole length at 50 m. The parametric analysis shows the influence of the ten examined parameters on the system’s performance and on the geothermal system characteristics. This work can be used as a reference study for the design and the investigation of future geothermal-driven CO2 heat pumps.

Analysis of Two-Phase Flow Solar Collectors With Application to Heat Pumps

1982 ◽  
Vol 104 (4) ◽  
pp. 358-365 ◽  
Author(s):  
S. K. Chaturvedi ◽  
Y. F. Chiang ◽  
A. S. Roberts
Keyword(s):  
Heat Pump ◽  
Thermal Performance ◽  
Two Phase Flow ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Phase Flow ◽  
Solar Collectors ◽  
Ambient Conditions ◽  
Two Phase

A thermodynamic model is developed to analyze the thermal performance of two-phase solar collectors. The well-known equilibrium homogeneous theory is used to model the two-phase flow in the solar collectors. The resultant set of coupled ordinary differential equations for saturated pressure and quality of working fluid in the collector tubes are solved by an iterative procedure using a fourth-order Runge-Kutta method. The results are then applied to determine the thermal performance of a solar assisted heat pump which uses two-phase flow collectors as the evaporator. The results indicate that even with the use of less expensive bare solar collectors as evaporator for the heat pump, the heating coefficient of performance (COPH) as high as 6 can be obtained under realistic ambient conditions provided a proper matching exists between the collector’s evaporative capacity and the compressor’s pumping capacity.

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