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 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 EXERGIC EFFICIENCY OF THE HEAT RECOVERY UNIT FOR WASTE GASES OF A HEAT ENGINE OF A COGENERATION PLANT

2020 ◽  
Vol 42 (3) ◽  
pp. 56-60
Author(s):  
N. Fialko ◽  
A. Stepanova ◽  
R. Navrodskaya ◽  
S. Shevchuk
Keyword(s):  
Heat Exchanger ◽  
Heat Recovery ◽  
Exergy Analysis ◽  
Heat Engine ◽  
Cogeneration Plant ◽  
Advantages And Disadvantages ◽  
Recovery Unit ◽  
Recovery Schemes ◽  
Exergy Losses ◽  
Complex Methods

The paper presents the results of a study of the efficiency of a heat recovery unit for waste gases of a heat engine of a cogeneration plant. The possibilities of using for this purpose the discrete-modular principle and complex methods of analyzing the efficiency of heat recovery systems, which are based on the methods of exergo-dissipative functions and exergic balances, are analyzed. The design features of the heat exchanger are considered and a conclusion is made about the possibility of presenting it as a system of eight discrete modules. The results of calculating the exergy characteristics for each of the eight heat exchanger modules, performed within the framework of the indicated methods, are presented. A regular decrease in exergy losses and heat-exergy criterion of efficiency is observed during the transition from the first to the eighth module of the heat recovery unit. However, exergy characteristics for the third and fourth modules of the heat exchanger are somewhat higher than the indicated dependence suggests. This indicates the thermodynamic imperfection of these modules. The main exergy losses in all heat exchanger modules are associated with losses due to heat transfer from flue gases to the wall. An insignificant discrepancy between the values ​​of the total exergy losses calculated within the framework of the methods used indicates that both methods can be used in various heat recovery schemes. However, in each specific case, it is necessary to choose a methodology with which it is possible to identify individual elements that need optimization or constructive improvement. Particular attention is paid to the comparative analysis of the selected techniques and consideration of the advantages and disadvantages of their use in various cases. It is noted that the technique based on the integral balance method of exergy analysis can be considered effective due to the small number of initial parameters and the simplicity of the analytical and calculation methods. The advantage of the technique using exergo-dissipative functions is that it allows one to differentiate exergy losses in a heat exchanger and establish the causes and areas of their localization.

Methodology for Intrinsic Exergy Analysis as Guide for Process Improvement With a Fuel Droplet Combustion Example

2005 ◽  
Author(s):  
Wladimir Sarmiento-Darkin ◽  
Noam Lior
Keyword(s):  
Process Improvement ◽  
Entropy Generation ◽  
Exergy Analysis ◽  
Combustion Process ◽  
Exergy Efficiency ◽  
Exergy Loss ◽  
System Level ◽  
Base Case ◽  
Droplet Combustion ◽  
Exergy Losses

While exergy analysis is by now commonly used on the system level to identify losses and recommend ways for reducing them, its use on the “intrinsic”, field, level where the exergy of a process is calculated as a function of location and time, is still developing. Intrinsic exergy analysis is a most useful method for identifying and understanding the specific reasons for exergy losses in a process, and in devising methods for their reduction. A good example, which is the sample case of this paper, is the analysis of exergy losses in combustion processes, which are known to be responsible for around 30 % of the fuel potential to produce power. In this paper we develop a methodology for intrinsic exergy analysis and for its use for process improvement, using the case of combustion of a n-heptane droplet as example. The time-dependent continuity, energy and species conservation equations together with the reaction kinetics, state equations, and temperature and concentration dependent transport properties, are solved numerically to determine the temperature and concentrations fields. These results are then used to calculate the rates of local entropy generation to determine the spatial and temporal irreversibilities produced during the combustion process, as well as the exergy efficiency. The results obtained indicate, among other things, that after ignition has taken place, the exergy loss (or entropy generation) component most responsible for the overall exergy loss is the chemical entropy, having the same order of magnitude as the rest of the entropy generation terms combined for all the cases evaluated. The computed exergy efficiency for the base case is 68.4%, in agreement with previous droplet combustion exergy studies. To develop guidelines for the process improvement, the sensitivity of the second law efficiency to the initial gas temperature (Tgi), reaction rate (ω), and combustion duration were analyzed. The results generated several promising improvement avenues.

Study on optimized adsorption chiller employing various heat and mass recovery schemes

2020 ◽  
Author(s):  
Mahbubul Muttakin ◽  
Md. Amirul Islam ◽  
Kuldeep Singh Malik ◽  
Deepak Pahwa ◽  
Bidyut Baran Saha
Keyword(s):  
Adsorption Chiller ◽  
Heat And Mass Recovery ◽  
Recovery Schemes ◽  
Mass Recovery

Simulation Study of the Heat and Mass Recovery on the Performance of Adsorption Cooling Systems

2014 ◽  
Author(s):  
K. C. Chan ◽  
C. Y. Tso ◽  
Christopher Y. H. Chao
Keyword(s):  
System Performance ◽  
Heat Recovery ◽  
Cooling System ◽  
Coefficient Of Performance ◽  
Cooling Power ◽  
Cooling Systems ◽  
Heating And Cooling ◽  
Adsorption Cooling System ◽  
Heat And Mass Recovery ◽  
Mass Recovery

In this study, simulation was conducted to investigate the effect of mass recovery, heat recovery, pre-heating and pre-cooling time on the system performance of a double-bed adsorption cooling system. Pressures of different system components were considered in the simulation. The adsorbent-adsorbate pair used was silica-gel and water. The heating and cooling temperatures were selected to be 85°C and 27°C respectively. Both the adsorption and desorption phase times were set at 15 minutes. The coefficient of performance (COP) and specific cooling power (SCP) were used to quantify the performance of the system. From the simulation, the basic cycle provided COP and SCP of 0.20 and 40.9W/kg respectively. By conducting heat recovery for 120 seconds, the system COP was largely increased by 99% to 0.40 compared to the basic cycle. The SCP was also increased to 42.3W/kg. Mass recovery, however, did not have too much effect on the system performance. The COP and SCP only increased by 4.5% and 3.9% respectively when conducting mass recovery for 4.7 seconds. For conducting heat and mass recovery, the COP and SCP were increased to 0.36 and 44.68W/kg, respectively. Pre-heating and pre-cooling can also be beneficial in improving both COP and SCP. The COP and SCP were increased by 14.5% and 10.1% respectively, to 0.23 and 45.0W/kg by conducting pre-heating and pre-cooling for 50.3 seconds. The combinations of these processes were also studied. It is suggested heat and mass recovery then pre-heating and pre-cooling should be conducted to improve COP and SCP. The improvements showed 31.2% for COP, increasing to 0.27, and 11.9% for SCP, increasing to 45.7W/kg.

EXERGY ANALYSIS OF GEOTHERMAL POWER PLANT KAMOJANG 68, 3 MW IN CAPACITY

2018 ◽  
Vol 7 (2) ◽  
Author(s):  
Amiral Aziz
Keyword(s):  
Energy Efficiency ◽  
Power Plant ◽  
Exergy Analysis ◽  
Exergy Efficiency ◽  
Preliminary Design ◽  
Exergy Destruction ◽  
Geothermal Power Plant ◽  
Production Wells ◽  
Geothermal Power ◽  
Exergy Losses

The importance of exergy analysis in preliminary design of geothermal power has been proven. An exergy analysis was carried out and the locations and quantities of exergy losses, wastes and destructions in the different processes of the plan were pinpointed. The obtained results show that the total exergy available from production wells KMJ 68 was calculated to be 6967.55 kW. The total exergy received from wells which is connected during the analysis and enter into the separator was found to be 6337.91 kW in which 5808.8 kW is contained in the steam phase. The overall exergy efficiency for the power plant is 43.06% and the overall energy efficiency is 13.05 %, in both cases with respect to the exergy from the connected wells. The parts of the system with largest exergy destruction are the condenser, the turbine, and the disposed waste brinekeywords: exergy, irreversibility, geothermal power plant, KMJ 68

scholarly journals Exergy analysis of marine waste heat recovery CO2 closed-cycle gas turbine system

Pomorstvo ◽  
2020 ◽  
Vol 34 (2) ◽  
pp. 309-322
Author(s):  
Vedran Mrzljak ◽  
Igor Poljak ◽  
Jasna Prpić-Oršić ◽  
Maro Jelić
Keyword(s):  
Gas Turbine ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Exergy Analysis ◽  
Waste Heat ◽  
Exergy Efficiency ◽  
Mechanical Power ◽  
Closed Cycle ◽  
Marine Waste

This paper presents an exergy analysis of marine waste heat recovery CO2 closed-cycle gas turbine system. Based on the operating parameters obtained in system exploitation, it is performed analysis of each system component individually, as well as analysis of the whole observed system. While observing all heat exchangers it is found that combustion gases-CO2 heat exchangers have the lowest exergy destructions and the highest exergy efficiencies (higher than 92%). The lowest exergy efficiency of all heat exchangers is detected in Cooler (51.84%). Observed system is composed of two gas turbines and two compressors. The analysis allows detection of dominant mechanical power producer and the dominant mechanical power consumer. It is also found that the turbines from the observed system have much higher exergy efficiencies in comparison to compressors (exergy efficiency of both turbines is higher than 94%, while exergy efficiency of both compressors did not exceed 87%). The whole observed waste heat recovery system has exergy destruction equal to 6270.73 kW, while the exergy efficiency of the whole system is equal to 64.12% at the selected ambient state. Useful mechanical power produced by the whole system and used for electrical generator drive equals 11204.80 kW. The obtained high exergy efficiency of the whole observed system proves its application on-board ships.

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.

Analysis of Energy and Exergy of an Annealing Furnace

2011 ◽  
Vol 110-116 ◽  
pp. 2156-2162 ◽  
Author(s):  
Md. Hasanuzzaman ◽  
R. Saidur ◽  
N.A. Rahim
Keyword(s):  
Flue Gas ◽  
Heat Recovery ◽  
Energy Savings ◽  
Cost Benefit ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Annealing Furnace ◽  
Energy And Exergy ◽  
Recovery System ◽  
Exergy Losses

Furnace is the most common and important part in metal industries. The useful concept of energy and exergy utilization is analyzed to investigate the energy and exergy efficiency, exergy losses, energy savings and cost benefit of an annealing furnace. The exergy efficiency of the combustor is found to be 47.05 %. The energy and exergy efficiencies of the annealing chamber are found to be 17.74 % and 12.86 % respectively. The overall energy and exergy efficiencies of the furnace are found to be 16.86 % and 7.30 % respectively. The annealing chamber is the major contributor for exergy destruction about 57 % of the annealing furnace. By using a heat recovery system from flue gas, about 8.11% of fuel can be saved within the payback period of less than 2 months.

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