EXERGY ANALYSIS OF A VAPOR COMPRESSION–VAPOR ABSORPTION CASCADE SYSTEM

2013 ◽  
Vol 21 (04) ◽  
pp. 1350026 ◽  
Author(s):  
GULSHAN SACHDEVA ◽  
VAIBHAV JAIN ◽  
S. S. KACHHWAHA
Keyword(s):  
Heat Exchanger ◽  
Cooling Capacity ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Vapor Compression ◽  
Cascade System ◽  
Structural Bond ◽  
Wide Range ◽  
Vapor Absorption ◽  
Absorption Section

In this paper, second law analysis has been done for the vapor compression–vapor absorption (VC–VA) cascade system. Ammonia–water is considered as the working pair in absorption section and R407C is dealt as the working fluid in VC section. Exergy destruction or the irreversibility rate is determined in each components of VC–VA cascade system, for a wide range of cooling capacity by considering a variable speed reciprocating compressor. Further in this, Coefficient of structural bond (CSB) analysis is carried out to quantify the effect of varying the generator temperature, effectiveness of solution heat exchanger, inlet temperature of external fluids in evaporator/condenser and some other variables. Solution heat exchanger and the condenser are reported to have high CSB value, so have a great scope of improvement to reduce the irreversibility rate of the whole system.

ENERGY ANALYSIS OF A VAPOR COMPRESSION SYSTEM CASCADED WITH AMMONIA–WATER ABSORPTION SYSTEM

2014 ◽  
Vol 22 (01) ◽  
pp. 1450007 ◽  
Author(s):  
GULSHAN SACHDEVA ◽  
VAIBHAV JAIN ◽  
S. S. KACHHWAHA
Keyword(s):  
Considerable Increase ◽  
Electricity Consumption ◽  
Cooling Capacity ◽  
Vapor Compression ◽  
Cascade System ◽  
Ammonia Water ◽  
Wide Range ◽  
Vapor Absorption ◽  
Condenser Temperature ◽  
Vapor Compression System

The first law analysis of a vapor compression–vapor absorption (VC–VA) cascade system is carried out for a wide range of cooling capacity. While ammonia–water is the working pair in VA section, R407C is used in VC section. The influences of change in cooling capacity, superheating and subcooling in the condenser, temperature in the generator, degree of overlap in cascade condenser, size of the heat exchangers etc. on the system performance are investigated. It is concluded that the COP of the VC section of the cascade system could be improved by 146% and the electricity consumption could be reduced by 64% compared to an equivalent VC unit. Separately the results showed the considerable increase in the generator heat when cooling capacity was increased from 83.33 kW. The COP of the cascade system at high cooling capacity is strongly dependent on the performance of condenser.

THE EFFECT OF LIQUID SUCTION HEAT EXCHANGER SUB-COOLER ON PERFORMANCE OF A FREEZER USING R404A AS WORKING FLUID

2015 ◽  
Vol 76 (11) ◽  
Author(s):  
Muhammad Nuriyadi ◽  
Sumeru Sumeru ◽  
Henry Nasution
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cooling Capacity ◽  
Experimental Results ◽  
Working Fluid ◽  
Liquid Line ◽  
Cabin Temperature

This study presents the effect of liquid-suction heat exchangers (LSHX) sub-cooler in a freezer. The LSHX sub-cooler is a method to increase the cooling capacity of the evaporator by lowering temperature at the condenser outlet. The decrease in temperature of the condenser outlet will cause a decrease in the quality refrigerant entering the evaporator. The lower the quality of the refrigerant entering the evaporator, the higher the cooling capacity produced by the evaporator. The LSHX sub-cooler utilizes a heat exchanger to transfer heat from the outlet of the condenser (liquid line) to the suction of the compressor. In the present study, three different LSHX sub-coolers in the freezer with cabin temperature settings of 0, -10 and -20oC were investigated. The results showed that the lowest and the highest of effectiveness of the heat exchanger were 0.28 and 0.58, respectively. The experimental results also showed that EER reduction is occurred at the cabin temperature setting of 0oC and -10oC, whereas the EER improvements were always occurred at the cabin temperature settings of -20oC.

scholarly journals Performance enhancement of an adsorption chiller by optimum cycle time allocation at different operating conditions

2019 ◽  
Vol 11 (10) ◽  
pp. 168781401988478
Author(s):  
M Gado ◽  
E Elgendy ◽  
Khairy Elsayed ◽  
M Fatouh
Keyword(s):  
Cycle Time ◽  
Time Allocation ◽  
Performance Enhancement ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Enhancement Ratio ◽  
Adsorption Chiller ◽  
Wide Range ◽  
Chilled Water

This article aims to improve the system cooling capacity of an adsorption chiller working with a silica gel/water pair by an allocation of the optimum cycle time at different operating conditions. A mathematical model was established and validated with the literature experimental data to predict the optimum cycle time for a wide range of hot (55°C–95°C), cooling (25°C–40°C), and chilled (10°C–22°C) water inlet temperatures. The optimum and conventional chiller performances are compared at different operating conditions. Enhancement ratio of the system cooling capacity was tripled as the cooling water inlet temperature increased from 25°C to 40°C at constant hot and chilled water inlet temperatures of 85°C and 14°C, respectively. Applying the concept of the optimum cycle time allocation, the system cooling capacity enhancement ratio can reach 15.6% at hot, cooling, and chilled water inlet temperatures of 95°C, 40°C, and 10°C, respectively.

Principles of Refrigerant Circuiting in Single Row Microchannel Evaporators

2013 ◽  
Author(s):  
Sunil Mehendale
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Predictive Ability ◽  
Element Model ◽  
Cooling Capacity ◽  
Fixed Number ◽  
Wide Range ◽  
First Pass ◽  
Louvered Fin

Microchannel evaporators are being increasingly considered for application in residential and commercial cooling and heat pump applications. This work analyzes the principles of refrigerant circuiting design in refrigerant-to-air heat exchangers using an element-by-element model developed for a microchannel evaporator. Geometric parameters such as microchannel tube depth, tube height, and port size, louvered fin density, louver angle, louver height, louver pitch, and fin height, as well as the air side face velocity, the refrigerant pressure-drop and heat transfer as a function of refrigerant mass flux are considered in the analysis. The model was first validated using data available in the open literature, thus providing a high level of confidence in the predictive ability of the model. Starting with a given microchannel tube and louvered fin geometry and a fixed number of tubes (and fins), the thermal performance of the heat exchanger was simulated over a wide range of two pass circuit configurations and tube lengths. It was found that the heat transfer versus pressure-drop trade-off provides an optimum relationship between the fraction of tubes in the first pass and the heat exchanger length. The sensitivity of the evaporator cooling capacity to the percentage of tubes in the first pass was also explored.

scholarly journals Selecting the Optimal Use of the Geothermal Energy Produced with a Deep Borehole Heat Exchanger: Exergy Performance

Proceedings ◽  
2020 ◽  
Vol 58 (1) ◽  
pp. 20
Author(s):  
Claudio Alimonti ◽  
Paolo Conti ◽  
Elena Soldo
Keyword(s):  
Heat Exchanger ◽  
Geothermal Energy ◽  
District Heating ◽  
High Energy ◽  
Exergy Efficiency ◽  
Deep Borehole ◽  
Borehole Heat Exchanger ◽  
Cascade System ◽  
Wide Range ◽  
Well Depth

The geothermal sector has a strength point with respect to other renewable energy sources: the availability of a wide range of both thermal and power applications depending on the source temperature. Several researches have been focused on the possibility to produce geothermal energy without brine extraction, by means of a deep borehole heat exchanger. This solution may be the key to increase the social acceptance, to reduce the environmental impact of geothermal projects, and to exploit unconventional geothermal systems, where the extraction of brine is technically complex. In this work, exergy efficiency has been used to investigate the best utilization strategy downstream of the deep borehole heat exchanger. Five configurations have been analyzed: a district heating plant, an absorption cooling plant, an organic Rankine cycle, a cascade system composed of district heat and absorption chiller, and a cascade system composed of the organic Rankine plant. District heating results in a promising and robust solution: it ensures high energy capacities per well depth and high exergy efficiency. Power production shows performances in line with typical geothermal binary plants, but the system capacity per well depth is low and the complexity increases both irreversibilities and sensibility to operative and source conditions.

Compact Diesel Engine Waste-Heat Driven Ammonia-Water Absorption Heat Pump Modeling and Performance Maximization Strategies

2021 ◽  
pp. 1-28
Author(s):  
Christopher M. Keinath ◽  
Jared Delahanty ◽  
Srinivas Garimella ◽  
Michael A. Garrabrant
Keyword(s):  
Heat Exchanger ◽  
Water Absorption ◽  
Heat Pump ◽  
Waste Heat ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Heat Transfer Fluid ◽  
Ammonia Water ◽  
Absorption Heat Pump ◽  
Wide Range

Abstract An investigation of the best ways to achieve optimal performance from a waste-heat-driven ammonia-water absorption heat pump over a wide range of operating conditions is presented. Waste-heat is recovered using an exhaust gas heat exchanger and delivered to the desorber by a heat transfer fluid loop. The absorber and condenser are hydronically coupled in parallel to an ambient heat exchanger for heat rejection. The evaporator provides chilled water for space-conditioning with a baseline cooling capacity of 2 kW. A detailed thermodynamics model is developed to simulate performance and develop strategies to achieve the best performance in both cooling and heating modes over a range of operating conditions. These parametric studies show that improved coefficients of performance can be achieved by adjusting the coupling fluid temperatures in the evaporator and the condenser/absorber as the ambient temperature varies. With the varying return temperatures, the system is able to provide the 2 kW design cooling capacity for a wide range of ambient temperatures.

scholarly journals The Increasing Role of Heat Exchangers in Gas Turbine Plants

1989 ◽  
Author(s):  
Colin F. McDonald
Keyword(s):  
Heat Exchanger ◽  
Gas Turbine ◽  
Heat Exchangers ◽  
Electrical Power ◽  
Plant Performance ◽  
Simple Cycle ◽  
Inlet Temperature ◽  
Full Spectrum ◽  
Wide Range ◽  
Prime Movers

In the introductory phase of gas turbine deployment for industrial service there was a natural reluctance to incorporate heat exchangers, although some variants included recuperators and intercoolers to enhance performance, since only modest values of compressor and turbine efficiency could be realized. Today, following half a century of intensive development, the situation is quite different, since high turbomachinery efficiencies contribute to attractive levels of performance for contemporary simple cycle plants. Because further aerodynamic advancements are likely to be incremental in nature, significant increase in plant performance can only be realized by either going to higher turbine inlet temperature, or utilizing more complex thermodynamic cycles, or both. It is in the latter two cases that heat exchangers will play an increasing role in the evolutionary advancement of gas turbine plant efficiency. This paper highlights the potential use of heat exchangers for a wide range of gas turbine applications, including industrial prime-movers, electrical power generation, marine service, and perhaps their ultimate use in aircraft propulsion systems. In the last decade, significant heat exchanger technology advancements have been made, to the point where previous impediments (to their widespread acceptance) associated with reliability, have been overcome. It is encouraging that today many proven heat exchanger hardware options are available to gas turbine users, and this will enhance their utilization across the full spectrum of applications, and indeed in the long-term may well make the simple cycle gas turbine obsolete.

scholarly journals Exergy destruction rate minimization in the absorber of a double effect vapor absorption system

2021 ◽  
pp. 222-222
Author(s):  
Muhammad Mushtaq ◽  
Muhammad Kamran ◽  
Haseeb Yaqoob ◽  
Muhammad Jamil ◽  
Muhammad Shafiq ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Energy Requirement ◽  
Double Effect ◽  
Cooling Capacity ◽  
Exergy Destruction ◽  
Absorption System ◽  
Destruction Rate ◽  
Penalty Factor ◽  
Vapor Absorption ◽  
Exergy Analyses

Despite the wide applications of multi-effect vapor absorption systems, their energy requirement is relatively higher. Also, their exergy analyses found in the literature reveal that the exergy destruction rate at the absorber is quite significant and has the potential for improvement in its energy efficiency. In this work, the exergy destruction rate at the absorber is minimized using the penalty factor method against the optimized generator temperature of the double-effect vapor absorption system by considering absorber, evaporator, and condenser temperatures into consideration. Modeling of the double-effect vapor absorption system was performed using a thermodynamic toolbox in SIMULINK. The present model employed a refrigerant heat exchanger to enhance the system cooling capacity. The Liquid-vapor ejector valve at the absorber also improved the mixing of the solution and refrigerant vapor resulting in lower irreversibility of the system. Results show that the coefficient of a performance increase by 2.4 % with refrigerant heat exchanger and exergy loss at absorber decrease by 9.4 % with ejector. The optimum performance was seen at the condenser and evaporator temperatures of 308.8 K and 278.1 K, respectively with an 8.2 % improvement in exergetic efficiency. Finally, it is concluded that the multi-effect absorption system shows better performance by minimizing the irreversibility.

The STEP 10 MWe sCO2 Pilot Demonstration Status Update

2020 ◽  
Author(s):  
John Marion ◽  
Brian Lariviere ◽  
Aaron McClung ◽  
Jason Mortzheim ◽  
Robin Ames
Keyword(s):  
Power Generation ◽  
Supercritical Co2 ◽  
Elevated Temperatures ◽  
Waste Heat ◽  
San Antonio ◽  
Test Facility ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Power Cycles ◽  
Wide Range

Abstract A team led by Gas Technology Institute (GTI®), Southwest Research Institute® (SwRI®) and General Electric Global Research (GE-GR), along with the University of Wisconsin and Natural Resources Canada (NRCan), is actively executing a project called “STEP” [Supercritical Transformational Electric Power project], to design, construct, commission, and operate an integrated and reconfigurable 10 MWe sCO2 [supercritical CO2] Pilot Plant Test Facility. The $122* million project is funded $84 million by the US DOE’s National Energy Technology Laboratory (NETL Award Number DE-FE0028979) and $38* million by the team members, component suppliers and others interested in sCO2 technology. The facility is currently under construction and is located at SwRI’s San Antonio, Texas, USA campus. This project is a significant step toward sCO2 cycle based power generation commercialization and is informing the performance, operability, and scale-up to commercial plants. Significant progress has been made. The design phase is complete (Phase 1) and included procurements of long-lead time deliver components. Now well into Phase 2, most major equipment is in fabrication and several completed and delivered. These efforts have already provided valuable project learnings for technology commercialization. A ground-breaking was held in October of 2018 and now civil work and the construction of a dedicated 25,000 ft2 building has progressed and is largely completed at the San Antonio, TX, USA project site. Supercritical CO2 (sCO2) power cycles are Brayton cycles that utilize supercritical CO2 working fluid to convert heat to power. They offer the potential for higher system efficiencies than other energy conversion technologies such as steam Rankine or Organic Rankine cycles this especially when operating at elevated temperatures. sCO2 power cycles are being considered for a wide range of applications including fossil-fired systems, waste heat recovery, concentrated solar power, and nuclear power generation. By the end of this 6-year STEP pilot demo project, the operability of the sCO2 power cycle will be demonstrated and documented starting with facility commissioning as a simple closed recuperated cycle configuration initially operating at a 500°C (932°F) turbine inlet temperature and progressing to a recompression closed Brayton cycle technology (RCBC) configuration operating at 715°C (1319 °F).

Effect of Gas Blockage on the Theoretical Performance of Thermoacoustic Refrigerators

2021 ◽  
Author(s):  
B. G. Prashantha ◽  
G. S. V. L. Narasimham ◽  
S. Seetharamu ◽  
K. Manjunatha
Keyword(s):  
Heat Exchanger ◽  
Cooling Capacity ◽  
Inert Gases ◽  
Environmentally Benign ◽  
Coefficient Of Performance ◽  
Vapor Compression ◽  
Simulation Results ◽  
The One ◽  
Thermoacoustic Refrigeration ◽  
Theoretical Performance

Thermoacoustic refrigeration is an emerging green, novel and promising alternate technology compared to vapor compression refrigerator systems for domestic cooling. It uses environmentally benign gases like air or helium or the mixture of inert gases as working substances and has no moving parts, no lubrication and no vibration. The cooler is designed and optimized with helium and air as refrigerants operating at 10[Formula: see text]bar with 3% drive ratio for the temperature difference of 28[Formula: see text]K and stack diameter of 200[Formula: see text]mm using linear thermoacoustic theory. In this paper, the effect of gas blockage (porosity) of the spiral-stack heat exchanger system ranging from 45% to 85% on the theoretical performance of the cooler is discussed. The one-third and one-fourth wavelength convergent–divergent resonator designs are optimized with air and helium as working substances, respectively, to improve performance and power density. The optimized coolers show best performance with 85% porosity. The theoretical results are validated with DeltaEC software simulation results. The simulation results show the coefficient of performance and cooling capacity of 0.93 and 219[Formula: see text]W for helium and of 0.50 and 139[Formula: see text]W for air, respectively, at the cold heat exchanger temperature of 0∘C.

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