scholarly journals Modeling of a Double Effect Heat Transformer Operating with Water/Lithium Bromide

Processes ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 371 ◽  
Author(s):  
Itzel N. Balderas-Sánchez ◽  
J. Camilo Jiménez-García ◽  
Wilfrido Rivera
Keyword(s):  
Lithium Bromide ◽  
Double Effect ◽  
Single Stage ◽  
Coefficient Of Performance ◽  
Generation Process ◽  
Absorption Process ◽  
Temperature Level ◽  
Stage System ◽  
Higher Temperature ◽  
Heat Transformer

Absorption heat transformers are effective systems for a wide variety of applications; however, their main purpose is to upgrade thermal energy from several sources at low-temperature up to a higher temperature level. In the literature, several advanced configurations for absorption heat transformers have been reported which are mainly focused on the improvement of the gross temperature lift by the use of a double absorption process; however, these systems usually offer a reduced coefficient of performance. The present study proposes a new advanced configuration of an absorption heat transformer that improves the coefficient of performance utilizing a double generation process. The operation of the new configuration was numerically modeled, and the main findings were discussed and presented emphasizing the effect of several parameters on the system performance. The highest coefficient of performance and gross temperature lift were 0.63 and 48 °C, respectively. From its comparison with a single-stage heat transformer, it is concluded that the proposed system may achieve coefficient of performance values up to 25.8% higher than those obtained with the single-stage system, although achieving lower gross temperature lifts.

Simulation of a Double-Effect Solar Absorption System for Traditional House in Yemen

2014 ◽  
Vol 695 ◽  
pp. 797-800 ◽  
Author(s):  
Osamah Zaid Ahmed ◽  
Farid Nasir Ani
Keyword(s):  
High Pressure ◽  
Lithium Bromide ◽  
Double Effect ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Absorption System ◽  
Alternative Source ◽  
Solar Absorption ◽  
Lithium Bromide Solution ◽  
Pressure Generator

During the last few years, the awareness of the pollution and the global warming has dramatically increased which encourage the researchers around the world to find an alternative source of energy. One of the most efficient sources of energy is the solar energy especially for cooling and heating applications. This paper, described the simulation of a double-effect solar absorption system in Yemen using water lithium bromide solution as a working fluid. The system will be applied to a typical traditional house in Yemen. The performance of the system will be analyzed based on different high pressure generator temperature for the yearly solar radiation data. At higher pressure generator temperature, the results show a higher coefficient of performance of the system. This simulation also estimate high pressure generator heat transfer required to operate the system. As a result, the size of solar collector area and the cost of such system will be calculated.

Design and Testing of an Augmented Generator for Solar Fired Absorption Chillers

Solar Energy ◽  
2003 ◽  
Author(s):  
James Bergquam ◽  
Joseph Brezner ◽  
Andrew Jensen
Keyword(s):  
Heat Transfer ◽  
Temperature Difference ◽  
Lithium Bromide ◽  
Double Effect ◽  
Coefficient Of Performance ◽  
Solar Collectors ◽  
Absorption Chiller ◽  
Pressurized Water ◽  
Absorption Chillers ◽  
Design And Testing

This paper presents results from a project sponsored by the California Energy Commission that involved the design and testing of an augmented generator for a solar fired, double effect absorption chiller. Solar powered absorption chillers use water heated by an array of solar collectors to boil a solution of lithium bromide and water. The energy transfer process between pressurized water heated by the solar collectors and the LiBr/H2O solution is the focus of this study. A method of augmenting the heat transfer in the generator was developed, bench tested and implemented in an operating 70kW solar HVAC system. The augmented design involved installing twisted stainless steel inserts in the tubes where the LiBr/H2O solution boils and refrigerant vapor is generated. The inserts increased the overall heat transfer coefficient between the heat medium in the shell side of the generator and the LiBr/H2O solution in the tubes. A solar-fired, double effect absorption chiller requires the collector array and storage tank to operate at temperatures in excess of 150°C. At these temperatures, the heating water must be at a pressure of about 700kPa to prevent it from boiling. This combination of high temperature and high pressure requires that the collectors, storage tanks, pumps, valves and piping be designed according to pressure vessel codes. This increases the initial cost of the system and also requires significant maintenance. The main objective of this work is to develop a method of lowering the requirements for a 150°C heating medium. The ultimate goal is to operate at about 120°C while maintaining the Coefficient of Performance and cooling capacity of the absorption chiller. The results presented in this paper show that the generator with twisted inserts can operate with an average log mean temperature difference of 10°C. The average COP of the chiller is about 1.0 and the chiller provided all of the cooling required by a 743 m2 building. Without the twisted inserts, the generator operated with a temperature difference of 22 to 28°C. The inserts provide significant reduction in the operating temperature of the solar collectors and do not adversely affect the performance of the double effect absorption chiller.

First and Second Law Analyses of Double Effect Parallel and Series Flow Direct Fired Absorption Cycles for Optimum Operating Parameters

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Md. Azhar ◽  
M. Altamush Siddiqui
Keyword(s):  
Volume Flow Rate ◽  
Minimum Energy ◽  
Lithium Bromide ◽  
Double Effect ◽  
Parallel Flow ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Optimum Operating ◽  
Liquefied Petroleum Gas ◽  
Flow Cycle

Thermodynamic analysis of double effect parallel and series flow direct fired absorption systems with lithium bromide–water has been carried out for different operating conditions. Temperatures in primary generator (Tg) and secondary generator (Tgs)/secondary condenser (Tcs) are optimized analytically using an iterative technique for maximum coefficient of performance (COP) and minimum energy required. A solution distribution ratio for a parallel flow cycle is also optimized. Source of energy used to drive the cycles is considered as compressed natural gas (CNG) and liquefied petroleum gas (LPG). Exergy destruction rate (EDR) in individual components as well as in the whole cycle along with volume flow rate of LPG and CNG is presented and compared. Results show that maximum COP for the parallel flow cycle is 3–6% higher than the series flow cycle. Also, minimum EDR of the parallel flow cycle is around 4% less while energy consumption is 2–3% low as compared to the series flow cycle.

Analysis of Aqueous Lithium Bromide Absorption Refrigeration Systems

2021 ◽  
pp. 1-18
Author(s):  
Dongchuan You ◽  
Hameed Metghalchi
Keyword(s):  
Lithium Bromide ◽  
Double Effect ◽  
Environmental Safety ◽  
Coefficient Of Performance ◽  
Low Grade ◽  
Absorption Refrigeration ◽  
Solution Energy ◽  
Exit Temperature ◽  
Single Effect ◽  
Aqueous Lithium Bromide

Abstract Aqueous lithium bromide absorption refrigeration systems have been studied in recent years and their advantages like environmental safety and utilization of low-grade energy have been proved. Research on improving their performance has been increasing lately. In this paper, single effect and parallel flow double-effect aqueous lithium bromide absorption refrigeration systems have been studied. Mass, energy, entropy and exergy balances have been used to model the absorption refrigeration systems. Parametric studies have been done to investigate effects of cooling load, evaporator exit temperature, condenser exit temperature, generator vapor exit temperature, absorber exit temperature, solution energy exchanger effectiveness on the performance of the system. The analyses show coefficient of performance and exergetic efficiency of double-effect absorption refrigeration is higher than those of a single-effect refrigeration. The effect of other parameters on performance of both single and double-effect systems have been described in detail in the article.

Absorption-Compression Heat Pump for Space Heating and Cooling Using Organic Fluids

2000 ◽  
Author(s):  
M. Nogues ◽  
M. Valles ◽  
M. Bourouis ◽  
D. Boer ◽  
A. Coronas
Keyword(s):  
Heat Pump ◽  
High Efficiency ◽  
Double Effect ◽  
Coefficient Of Performance ◽  
Space Heating ◽  
Solution Flow Rate ◽  
Cooling Power ◽  
Heating And Cooling ◽  
Higher Temperature ◽  
Single Effect

Abstract The combination of compression and absorption technologies can provide heat pumps with high efficiency and a wide operating range. The aim of this research project lies in the development and testing of a gas-fired double effect absorption-compression heat pump working with organic pairs for space heating and cooling. For these applications, the use of suitable organic working pairs makes possible heat pump operation at higher temperature lifts than that of conventional water-lithium bromide systems. In our research, the combination Methanol and Tetraethylenglycoldimethylether (TEGDME) has been selected as working pair. The heat pump is targeted to operate in both cooling and heating modes. Therefore, the basic structure of the heat pump is an absorption-compression double effect cycle for cooling mode, that can be switched to a single effect cycle, in order to achieve the required higher temperature lift for the heating operation. The nominal working conditions for cooling are 5°C at the evaporator and 35 to 45°C at me absorber-condenser. These conditions can be achieved with a double effect absorption-compression cycle. Different solution circuit flow configurations as serial, parallel and reverse flow have been considered. The heating operation of the heat pump aims at a temperature of the useful delivered heat between 45 and 60°C for an evaporator temperature of 0°C. In order to achieve the required temperature lift with an attractive performance (COP in the heating mode higher than unity), the unit should operate as a single effect absorption-compression heat pump. The performance analysis was based on a thermodynamic model considering the equilibrium properties of the working pair and energy and mass balances in the different components. Results in both operating modes have been evaluated in terms of the solution flow rate, the coefficient of performance COP and the primary energy ratio PER. Very interesting performances are found even for high temperature lifts. The serial flow configuration has been selected due to its good performance and technological aspects. This work forms part of the project CLIMABGAS. A prototype of this heat pump is under construction for a cooling power of 20 kW and a heating power of 24.5 kW.

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