scholarly journals Energy and Exergy Analyses of Adsorption Chiller at Various Recooling-Water and Dead-State Temperatures

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2172
Author(s):  
Ahmad A. Alsarayreh ◽  
Ayman Al-Maaitah ◽  
Menwer Attarakih ◽  
Hans-Jörg Bart
Keyword(s):  
Water Temperature ◽  
Recovery Time ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Adsorption Chiller ◽  
Dead State ◽  
Energy And Exergy ◽  
The Dead ◽  
Exergy Analyses ◽  
Mass Recovery

We conducted energy and exergy analyses of an adsorption chiller to investigate the effect of recooling-water temperatures on the cooling capacity and Coefficient of Performance (COP) with variable cycle modes. We investigated both the effect of the recooling-water temperature and the dead state temperature on the exergy destruction in the chiller components. Our results show that there is an optimum reheat cycle mode for each recooling-water temperature range. For the basic single stage cycle, the exergy destruction is mainly accrued in the desorber (49%), followed by the adsorber (27%), evaporator (13%), condenser (9%), and expansion valve (2%). The exergy destruction for the preheating process is approximately 35% of the total exergy destruction in the desorber. By contrast, the precooling process is almost 58% of the total exergy destruction in the adsorber. The exergy destruction decreases when increasing the recooling-water and the dead state temperatures, while the exergy efficiency increases. Nonetheless, the exergy efficiency decreases with an increase in the recooling-water temperature at fixed dead state temperatures. The effect of the mass recovery time in the reheat cycle on exergy destruction was also investigated, and the results show that the exergy destruction increases when the mass recovery time increases. The exergy destruction in the adsorbent beds was the most sensitive to the increase in mass recovery time.

scholarly journals Exergy Analysis of Advanced Adsorption Cooling Cycles

Entropy ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1082
Author(s):  
Ngoc Vi Cao ◽  
Xuan Quang Duong ◽  
Woo Su Lee ◽  
Moon Yong Park ◽  
Seung Soo Lee ◽  
...  
Keyword(s):  
Recovery Time ◽  
Heat Recovery ◽  
Exergy Analysis ◽  
Exergy Efficiency ◽  
Recovery Cycle ◽  
Adsorption Chiller ◽  
Advanced Cycles ◽  
Heat And Mass Recovery ◽  
Exergy Losses ◽  
Mass Recovery

This study conducted an exergy analysis of advanced adsorption cooling cycles. The possible exergy losses were divided into internal losses and external losses, and the exergy losses of each process in three advanced cycles: a mass recovery cycle, heat recovery cycle and combined heat and mass recovery cycle were calculated. A transient two-dimensional numerical model was used to solve the heat and mass transfer kinetics. The exergy destruction of each component and process in a finned tube type, silica gel/water working paired-adsorption chiller was estimated. The results showed that external loss was significantly reduced at the expense of internal loss. The mass recovery cycle reduced the total loss to 60.95 kJ/kg, which is −2.76% lower than the basic cycle. In the heat recovery cycle, exergy efficiency was significantly enhanced to 23.20%. The optimum value was 0.1248 at a heat recovery time of 60 s. The combined heat and mass recovery cycle resulted in an 11.30% enhancement in exergy efficiency, compared to the heat recovery cycle. The enhancement was much clearer when compared to the basic cycle, with 37.12%. The observed dependency on heat recovery time and heating temperature was similar to that observed for individual mass recovery and heat recovery cycles.

scholarly journals Energy and exergy analysis of combined cooling and power system using variable mode adsorption chiller

2021 ◽  
Vol 294 ◽  
pp. 03002
Author(s):  
Ahmad A. Alsarayreh ◽  
Ayman Al-Maaitah ◽  
Menwer Attarakih ◽  
Hans-Jörg Bart
Keyword(s):  
Ambient Temperature ◽  
Waste Heat ◽  
Exergy Efficiency ◽  
Single Stage ◽  
Ambient Conditions ◽  
Adsorption Chiller ◽  
Energy And Exergy ◽  
Variable Mode ◽  
Combined Cooling ◽  
Mass Recovery

Adsorption cooling is a promising technology to recover low-temperature waste heat from a diesel genset. In this paper, an advanced adsorption chiller working in variable mode is proposed for the combined cooling and power cycle (CCP) to recover waste heat from the water jacket in the diesel genset. The chiller works on three modes based on the ambient temperature for better heat utilization. In this study, three modes were investigated: single-stage cycle mode, short-duration, and medium-duration mass recovery modes. The results show that the energy and exergy efficiency for a single-stage cycle mode is higher at an ambient temperature lower than 35 °C . In comparison, the mass recovery mode has a higher energy and exergy efficiency at an ambient temperature higher than 35 °C. The annual energy and exergy efficiency for the CCP was investigated when the chiller works with variable modes based on the ambient temperature under DUBAI weather conditions as a case study. The results show an improvement of 14.7% and 14% of the energy and exergy efficiency, respectively, for CCP with a variable mode adsorption chiller compared to diesel genset alone. The results also show the CCP with variable mode adsorption chiller has a slight improvement on both energy and exergy efficiency compared to CCP with a single-stage adsorption chiller at the same ambient conditions.

Energy and Exergy Assessments of a New Trigeneration System Based on Organic Rankine Cycle and Biomass Combustor

2010 ◽  
Author(s):  
Fahad A. Al-Sulaiman ◽  
Feridun Hamdullahpur ◽  
Ibrahim Dincer
Keyword(s):  
Electrical Power ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Exergy Efficiency ◽  
Heating Process ◽  
Inlet Temperature ◽  
Exergy Destruction ◽  
Energy And Exergy ◽  
Pump Inlet ◽  
Exergy Analyses

In this paper, energy and exergy analyses of a trigeneration system based on an organic Rankine cycle (ORC) and a biomass combustor are presented. This trigeneration system consists of a biomass combustor to provide heat input to the ORC, an ORC for power production, a single-effect absorption chiller for cooling process and a heat exchanger for heating process. The system is designed to produce around 500 kW of electricity. In this study, four cases are considered, namely, electrical-power, cooling-cogeneration, heating-cogeneration and trigeneration cases. The effects of changing ORC pump inlet temperature and turbine inlet pressure on different key parameters have been examined to evaluate the performance of the trigeneration system. These parameters are energy and exergy efficiencies, electrical to cooling ratio and electrical to heating ratio. Moreover, exergy destruction analysis is presented to show the main sources of exergy destruction and the contribution of each source to the exergy destruction. The study shows that there are significant improvements in energy and exergy efficiencies when trigeneration is used as compared to electrical power. The results show that the maximum efficiencies for the cases considered in this study are as follows: 14.0% for electrical power, 17.0% for cooling cogeneration, 87.0% for heating cogeneration and 89.0% for trigeneration. On other hand, the maximum exergy efficiency of the ORC is 13.0% while the maximum exergy efficiency of the trigeneration system is 28.0%. In addition, this study reveals that the main sources of exergy destruction are the biomass combustor and ORC evaporator.

scholarly journals Exergy efficiency of thermochemical syngas-to-ethanol production plants

2021 ◽  
Vol 3 (5) ◽  
Author(s):  
Marcos Paulo Gabriel da Costa e Silva ◽  
Júlio Cesar de Carvalho Miranda
Keyword(s):  
Ethanol Production ◽  
Process Improvement ◽  
Second Generation ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Exothermic Reactions ◽  
Production Processes ◽  
Different Temperatures ◽  
Exergy Analyses ◽  
Second Generation Ethanol

Abstract This work presents exergy analyses applied in four different conceptual second-generation ethanol production processes through a thermochemical route using catalysts based on Molybdenum (P-1), Copper (P-2), and Rhodium (P-3 and P-4), aiming to assess their exergetic efficiencies. The results show that the conceptual processes have satisfactory exergy efficiencies in both cases, when compared among themselves and when compared with other processes reported in literature. The processes’ efficiency for P-1, P-2, P-3 and P-4 were, respectively, 52.4%, 41.4%, 43.7% and 48.9%. The reactors were the sections in which exergy destruction was more significant, due to the exothermic reactions and mixing points (where streams with different temperatures were mixed). Such results show the potential of thermochemical ethanol production, besides opening the possibilities of process improvement. Graphic abstract

scholarly journals Energy and Exergy Analyses of Tube Banks in Waste Heat Recovery Applications

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2094 ◽  
Author(s):  
Mustafa Erguvan ◽  
David MacPhee
Keyword(s):  
Energy Efficiency ◽  
Reynolds Number ◽  
Heat Recovery ◽  
Waste Heat ◽  
Cross Flow ◽  
Exergy Efficiency ◽  
Circular Cylinders ◽  
Published Data ◽  
Energy And Exergy ◽  
Exergy Analyses

In this study, energy and exergy analyses have been investigated numerically for unsteady cross-flow over heated circular cylinders. Numerous simulations were conducted varying the number of inline tubes, inlet velocity, dimensionless pitch ratios and Reynolds number. Heat leakage into the domain is modeled as a source term. Numerical results compare favorably to published data in terms of Nusselt number and pressure drop. It was found that the energy efficiency varies between 72% and 98% for all cases, and viscous dissipation has a very low effect on the energy efficiency for low Reynolds number cases. The exergy efficiency ranges from 40–64%, and the entropy generation due to heat transfer was found to have a significant effect on exergy efficiency. The results suggest that exergy efficiency can be maximized by choosing specific pitch ratios for various Reynolds numbers. The results could be useful in designing more efficient heat recovery systems, especially for low temperature applications.

Climatic Effect on the Exergetic Performance of Conventional to Hybrid Evaporative Coolers with Varying Dead State Temperatures in India

2021 ◽  
pp. 1-33
Author(s):  
V Venkateswara Rao ◽  
Santanu Prasad Datta
Keyword(s):  
Air Conditioning ◽  
Sustainability Assessment ◽  
Cooling System ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Direct Expansion ◽  
Dead State ◽  
Evaporative Cooling System ◽  
Expansion Cooling ◽  
Semi Arid

Abstract A comprehensive exergy, exergo-economic and sustainability assessment of seven conventional to hybrid air-conditioning systems comprising direct and indirect evaporative coolers with direct expansion system, and their several combinations integrated into an 8-story domestic building for 5 different cities corresponding to arid, semi-arid, humid sub-tropical, tropical wet and dry, and tropical wet climatic zones across India are investigated based on simulation output from EnergyPlus. The exergetic performances are reported for varying dead state temperatures ranging from 5°C to 40°C while saturated humidity ratio and pressure at system outlet are two other dead state properties. The results reveal that the specific exergy of moist air and exergetic efficiency decrease with increasing dead state temperature and become least at a dead state temperature near to American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE) comfort temperature of 23°C. In arid, semi-arid and humid subtropical climates, the three-stage evaporative cooling system exhibited the lowest exergy destruction of 100 J kg−1 and the highest exergy efficiency of 90% at a dead state temperature of 40°C. The two-stage direct evaporative-direct expansion cooling system exhibited superior exergy efficiency of around 90% in tropical wet and dry and tropical wet zones. Further, the Grassmann diagram based on the climate of Hyderabad indicated that the three-stage cooling system is energetically and exergetically optimum with exergy destruction of 28.86%.

First and second thermodynamic law analyses applied to a solar dish collector

2014 ◽  
Vol 39 (4) ◽  
Author(s):  
Vahid Madadi ◽  
Touraj Tavakoli ◽  
Amir Rahimi
Keyword(s):  
Heat Transfer ◽  
Solar Radiation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Flow Rates ◽  
Energy And Exergy ◽  
Mass Flow Rates

AbstractThe energy and exergy performance of a parabolic dish collector is investigated experimentally and theoretically. The effect of receiver type, inlet temperature and mass flow rate of heat transfer fluid (HTF), receiver temperature, receiver aspect ratio and solar radiation are investigated. To evaluate the effect of the receiver aperture area on the system performance, three aperture diameters are considered. It is deduced that the fully opened receivers have the greatest exergy and thermal efficiency. The cylindrical receiver has greater energy and exergy efficiency than the conical one due to less exergy destruction. It is found that the highest exergy destruction is due to heat transfer between the sun and the receivers and counts for 35 % to 60 % of the total wasted exergy. For three selected receiver aperture diameters, the exergy efficiency is minimum for a specified HTF mass flow rate. High solar radiation allows the system to work at higher HTF inlet temperatures. To use this system in applications that need high temperatures, in cylindrical and conical receivers, the HTF mass flow rates lower than 0.05 and 0.09 kg/s are suggested, respectively. For applications that need higher amounts of energy content, higher HTF mass flow rates than the above mentioned values are recommended.

Energy and exergy analyses of coconut drying in a solar tunnel drier

2021 ◽  
pp. 095440892110053
Author(s):  
S Ayyappan ◽  
M Selvakumar ◽  
T Ram Kumar
Keyword(s):  
Moisture Content ◽  
Initial Moisture Content ◽  
Second Law Of Thermodynamics ◽  
Exergy Efficiency ◽  
Energy Utilization ◽  
Exergy Loss ◽  
Air Velocity ◽  
Tunnel Drier ◽  
Energy And Exergy ◽  
Exergy Analyses

This paper presents energy and exergy analyses of solar drying of coconuts in a hemispherical solar tunnel drier. Coconuts were dried from an initial moisture content of about 55% (w.b.) to 7% (w.b.) in the solar tunnel drier in 60 hrs whereas the open sun drying process takes 153 hrs for reducing the moisture content to the same level. The drying experiments were conducted at a mass flow rate of 7.25 kg/s with an average air velocity of 0.1 m/s. Using the first law of thermodynamics, energy analysis was carried out to estimate the amount of energy received by the solar tunnel drier and the ratios of energy utilization. However, exergy analysis was accomplished to determine the exergy loss and exergy efficiency by applying the second law of thermodynamics. Energy utilization, energy utilization ratio, exergy inflow and exergy loss in the drier were studied and these values are found to be increased with increasing solar radiation. The exergy inflow and exergy loss in the drier varied between 0.194 kJ/s–8.18 kJ/s and 0.085 kJ/s–5.377 kJ/s respectively. The exergy efficiency of the drier varied between 23.6%–53%.

scholarly journals Performance Analysis of Variable Mode Adsorption Chiller at Different Recooling Water Temperatures

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3871
Author(s):  
Ahmad A. Alsarayreh ◽  
Ayman Al-Maaitah ◽  
Menwer Attarakih ◽  
Hans-Jörg Bart
Keyword(s):  
Experimental Data ◽  
Water Temperature ◽  
Cycle Time ◽  
Single Stage ◽  
Force Model ◽  
Technical Problems ◽  
Cooling Cycle ◽  
Adsorption Chiller ◽  
Variable Mode ◽  
Mass Recovery

Adsorption cooling can recover waste heat at low temperature levels, thereby saving energy and reducing greenhouse gas emissions. An air-cooled adsorption cooling system reduces water consumption and the technical problems associated with wet-cooling systems; however, it is difficult to maintain a constant recooling water temperature using such a system. To overcome this limitation, a variable mode adsorption chiller concept was introduced and investigated in this study. A prototype adsorption chiller was designed and tested experimentally and numerically using the lumped model. Experimental and numerical results showed good agreement and a similar trend. The adsorbent pairs investigated in this chiller consisted of silicoaluminophosphate (SAPO-34)/water. The experimental isotherm data were fitted to the Dubinin–Astakhov (D–A), Freundlich, Hill, and Sun and Chakraborty (S–C) models. The fitted data exhibited satisfactory agreement with the experimental data except with the Freundlich model. In addition, the adsorption kinetics parameters were calculated using a linear driving force model that was fitted to the experimental data with high correlation coefficients. The results show that the kinetics of the adsorption parameters were dependent on the partial pressure ratio. Four cooling cycle modes were investigated: single stage mode and mass recovery modes with duration times of 25%, 50%, and 75% of the cooling cycle time (denoted as short, medium, and long mass recovery, respectively). The cycle time was optimized based on the maximum cooling capacity. The single stage, short mass recovery, and medium mass recovery modes were found to be the optimum modes at lower (<35 °C), medium (35–44 °C), and high (>44 °C) recooling temperatures. Notably, the recooling water temperature profile is very important for assessing and optimizing the suitable working mode.

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