scholarly journals Performance Enhancement of Hybrid Solid Desiccant Cooling Systems by Integrating Solar Water Collectors in Taiwan

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3470 ◽  
Author(s):  
Win-Jet Luo ◽  
Dini Faridah ◽  
Fikri Rahmat Fasya ◽  
Yu-Sheng Chen ◽  
Fikri Hizbul Mulki ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Performance Enhancement ◽  
Cooling System ◽  
Critical Value ◽  
Coefficient Of Performance ◽  
Outdoor Temperature ◽  
Heated Water ◽  
Vapor Compression System ◽  
Residential Air Conditioning ◽  
Air Conditioning Systems

A hybrid solid desiccant cooling system (SDCS), which combines a solid desiccant system and a vapor compression system, is considered to be an excellent alternative for commercial and residential air conditioning systems. In this study, a solar-assisted hybrid SDCS system was developed in which solar-heated water is used as an additional heat source for the regeneration process, in addition to recovering heat from the condenser of an integrated heat pump. A solar thermal collector sub-system is used to generate solar regeneration water. Experiments were conducted in the typically hot and humid weather of Taichung, Taiwan, from the spring to fall seasons. The experimental results show that the overall performance of the system in terms of power consumption can be enhanced by approximately 10% by integrating a solar-heated water heat exchanger in comparison to the hybrid SDCS system. The results show that the system performs better when the outdoor humidity ratio is large. In addition, regarding the effect of ambient temperature on the coefficient of performance (COP) of the systems, a critical value of outdoor temperature exists. The COP of the systems gradually rises with the increase in ambient temperature. However, when the ambient temperature is greater than the critical value, the COP gradually decreases with the increase in ambient temperature. The critical outdoor temperature of the hybrid SDCS is from 26 °C to 27 °C, and the critical temperature of the solar-assisted hybrid SDCS is from 27 °C to 30 °C.

Optimized Refrigerant Flow Rate and Dimensions of the Ejector Employed in a Modified Ejector Vapor Compression System

2020 ◽  
Vol 28 (04) ◽  
pp. 2050038
Author(s):  
Dishant Sharma ◽  
Gulshan Sachdeva ◽  
Dinesh Kumar Saini
Keyword(s):  
Flow Rate ◽  
Cooling System ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Vapor Compression ◽  
Evaporator Temperature ◽  
Proposed Model ◽  
Condenser Temperature ◽  
Vapor Compression System ◽  
Vapor Compression Cooling

This paper presents the analysis of a modified vapor compression cooling system which uses an ejector as an expansion device. Expanding refrigerant in an ejector enhances the refrigeration effect and reduces compressor work. Therefore, it yields a better coefficient of performance. Thermodynamic analysis of a constant area ejector model has been done to obtain primary dimensions of the ejector for given condenser and evaporator temperature and cooling capacity. The proposed model has been used to design the ejector for three refrigerants; R134a, R152a and R1234yf. The refrigerant flow rate and the diameters at various sections of the ejector have been obtained by doing numerical modeling in Engineering Equation Solver (EES). Refrigerant R1234yf demanded the highest diameter requirements at a fixed 5∘C evaporator temperature and 40∘C condenser temperature for a given range of cooling load. Both primary and secondary refrigerants flow rates are higher for R1234yf followed by R134a and then R152a.

scholarly journals Next-Generation HVAC: Prospects for and Limitations of Desiccant and Membrane-Based Dehumidification and Cooling

2017 ◽  
Author(s):  
Omar Labban
Keyword(s):  
Cooling System ◽  
System Level ◽  
Device Performance ◽  
Vapor Compression ◽  
Next Generation ◽  
Outdoor Temperature ◽  
Cooling Process ◽  
Vapor Compression System ◽  
Shed Light ◽  
Specific Technology

Recently, next-generation HVAC technologies have gained attention as potential alternatives to the conventional vapor-compression system (VCS) for dehumidification and cooling. Previous studies have primarily focused on analyzing a specific technology or its application to a particular climate. A comparison of these technologies is necessary to elucidate the reasons and conditions under which one technology might outperform the rest. In this study, we apply a uniform framework based on fundamental thermodynamic principles to assess and compare different HVAC technologies from an energy conversion standpoint. The thermodynamic least work of dehumidification and cooling is formally defined as a thermodynamic benchmark, while VCS performance is chosen as the industry benchmark against which other technologies, namely desiccant-based cooling system (DCS) and membrane-based cooling system (MCS), are compared. The effect of outdoor temperature and humidity on device performance is investigated, and key insights underlying the dehumidification and cooling process are elucidated. In spite of the great potential of DCS and MCS technologies, our results underscore the need for improved system-level design and integration if DCS or MCS are to compete with VCS. Our findings have significant implications for the design and operation of next-generation HVAC technologies and shed light on potential avenues to achieve higher efficiencies in dehumidification and cooling applications.

scholarly journals An Optimal Air-Conditioner On-Off Control Scheme under Extremely Hot Weather Conditions

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1021 ◽  
Author(s):  
Mohammed Al-Azba ◽  
Zhaohui Cen ◽  
Yves Remond ◽  
Said Ahzi
Keyword(s):  
Ambient Temperature ◽  
Weather Conditions ◽  
Online Optimization ◽  
Coefficient Of Performance ◽  
Control Technique ◽  
Air Conditioner ◽  
Outdoor Temperature ◽  
Temperature Variations ◽  
Wide Range ◽  
Hot Weather

Being reliant on Air Conditioning (AC) throughout the majority of the year, desert countries with extremely hot weather conditions such as Qatar are facing challenges in lowering weariness cost due to AC On-Off switching while maintaining an adequate level of comfort under a wide-range of ambient temperature variations. To address these challenges, this paper investigates an optimal On-Off control strategy to improve the AC utilization process. To overcome complexities of online optimization, a Elman Neural Networks (NN)-based estimator is proposed to estimate real values of the outdoor temperature, and make off-line optimization available. By looking up the optimum values solved from an off-line optimization scheme, the proposed control solutions can adaptively regulate the indoor temperature regardless of outdoor temperature variations. In addition, a cost function of multiple objectives, which consider both Coefficient of Performance (COP), and AC compressor weariness due to On-Off switching, is designed for the optimization target of minimum cost. Unlike conventional On-Off control methodologies, the proposed On-Off control technique can respond adaptively to match large-range (up to 20 ∘ C) ambient temperature variations while overcoming the drawbacks of long-time online optimization due to heavy computational load. Finally, the Elman NN based outdoor temperature estimator is validated with an acceptable accuracy and various validations for AC control optimization under Qatar’s real outdoor temperature conditions, which include three hot seasons, are conducted and analyzed. The results demonstrate the effectiveness and robustness of the proposed optimal On-Off control solution.

scholarly journals Energy-Saving Potential of Thermal Diode Tank Assisted Refrigeration and Air-Conditioning Systems

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 206
Author(s):  
Mingzhen Wang ◽  
Eric Hu ◽  
Lei Chen
Keyword(s):  
Ambient Temperature ◽  
Energy Saving ◽  
Air Conditioning ◽  
Coefficient Of Performance ◽  
Weather Data ◽  
Water Tank ◽  
Previous Night ◽  
Baseline System ◽  
Save Energy ◽  
Air Conditioning Systems

Lowering the condensing temperature of the Refrigeration and Air-conditioning (RAC) system has been proven to effectively increase the system’s Coefficient of Performance (COP). This paper revolves around evaluating the energy-saving generated by applying a Thermal Diode Tank (TDT) in the RAC systems. The TDT is a novel invention, which is an insulated water tank equipped with gravity heat pipes. If the TDT was placed outdoors overnight, its inside water would theoretically be at the minimum ambient temperature of the previous night. When the TDT water is used to cool the condenser of RAC systems that operate during the daytime, a higher COP of this TDT assisted RAC (TDT-RAC) system could be achieved compared with the baseline system. In this study, a steady-state performance simulation model for TDT-RAC cycles has been developed. The model reveals that the COP of the TDT-RAC cycle can be improved by 10~59% over the baseline cycle depending on the compressor types. The TDT-RAC cycle with a variable speed compressor can save more energy than that with a fixed speed compressor. In addition, TDT-RAC cycles can save more energy with a higher day/night ambient temperature difference. There is a threshold tank size for a given TDT-RAC cycle to save energy, and the energy-saving can be improved by enlarging the tank size. A desk-top case study based on real weather data for Adelaide in January 2021 shows that 9~40% energy could be saved by TDT-RAC systems every summer day on average.

Optimization of a Thermoelectric Air Conditioning Systems

2013 ◽  
Vol 336 ◽  
pp. 111-120
Author(s):  
Jamir Machado da Silva ◽  
Renan Eduardo da Silva ◽  
José Rui Camargo ◽  
Ederaldo Godoy Junior
Keyword(s):  
Cooling System ◽  
Thermoelectric Module ◽  
Electrical Current ◽  
Coefficient Of Performance ◽  
Thermoelectric Cooling ◽  
Thermoelectric Modules ◽  
Air Inlet ◽  
The One ◽  
Air Conditioning Systems ◽  
Cooling Air

This paper studies the optimization of a thermoelectric cooling system of air. Based on both results obtained experimentally and from a mathematical model, we evaluated the available features of thermoelectric modules and parameters subject to optimization. In the thermoelectric cooling air process based on the effect discovered by Jean Peltier Charles Athanase in 1834, when an electrical current is conducted through a semiconductor junction between two materials with different properties, heat is absorbed and dissipated. Thermoelectric modules are made of semiconductor materials and sealed between two plates. According to the shape of the plate, the current flow cools the one hand and the other is heated. The most important parameters to evaluate the efficiency of the thermoelectric cooling is the coefficient of performance, the rate of heat transfer and temperature difference between the maximum possible to the cold and hot sides of the thermoelectric module. In this evaluation were used thermoelectric modules and heat sinks, commercially available temperature sensors and a software for obtaining, storing and comparing the data. The prototype auxiliary allows the surface temperatures of thermoelectric modules of the hot and cold sides, the air inlet and outlet temperatures of the heat sink sides of the hot and cold air flow, the voltage and the electrical current to be applied to the modules. A simulation is performed using two air flows at a speed controlled for the hot and cold sides of the module and a set of tests for various modules, i.e. one, two, three and four coupled in parallel. Using this system, the performance data is analyzed making it possible to check the power, voltage and electrical current to maximize the coefficient of performance of the system.

Experimental Investigation of a Miniature Ejector Using Water As Working Fluid

2019 ◽  
Author(s):  
Jingming Dong ◽  
Yuxin Xia ◽  
Hongbin Ma ◽  
He Song ◽  
Zhongxi Zhao ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
High Temperature ◽  
Ambient Temperature ◽  
Working Conditions ◽  
Nozzle Exit ◽  
Cooling System ◽  
Area Ratio ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Condensing Pressure

Abstract This paper presents an experimental investigation of a miniature ejector using water as the working fluid. The investigated ejector cooling system can be used to keep the temperature of an electric chip below ambient temperature. The authors tested the effects of working conditions, the nozzle exit position (NXP), and the area ratio on the ejector’s performance. Experimental results show that the miniature ejector works well in the high-temperature evaporator (HTE) under temperatures ranging from 55 °C to 70 °C and can achieve a 0.66 coefficient of performance (COP). With the increase of the NXP, the COP decreased, while the critical condensing pressure first increased and then decreased. As the area ratio of the miniature ejector increased, the COP increased, and the critical condensing pressure decreased.

Parametric Study of Inlet Cooling With Varied COP on Gas Turbine Performance

2014 ◽  
Author(s):  
Maryam Besharati-Givi ◽  
Xianchang Li
Keyword(s):  
Ambient Temperature ◽  
Gas Turbine ◽  
Power Output ◽  
Gas Turbines ◽  
High Efficiency ◽  
Cooling System ◽  
Coefficient Of Performance ◽  
Inlet Temperature ◽  
Turbine Performance ◽  
Compressor Inlet

Gas turbines play an important role in power generation, and it is therefore desired to operate gas turbines with high efficiency and power output. One of the most influential parameters on the performance of a gas turbine is the ambient condition. It is known that inlet cooling can improve the gas turbine performance, especially when the ambient temperature is high. This study examines the effect of inlet cooling with different operating parameters such as compressor inlet temperature, turbine inlet temperature, air fuel ratio, and pressure ratio. Furthermore, the coefficient of performance (COP) of the cooling system is considered a function of the ambient temperature. Aspen Plus software is used to simulate the system under a steady-flow condition. The results indicate that the cooling of the compressor inlet air can substantially improve the power output as well as the overall efficiency of system. More importantly, there exists an optimal temperature at which the inlet cooling should be operated to achieve the highest efficiency.

scholarly journals Dehumidification Potential of a Solid Desiccant Based Evaporative Cooling System with an Enthalpy Exchanger Operating in Subtropical and Tropical Climates

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2704 ◽  
Author(s):  
Ramadas Narayanan ◽  
Edward Halawa ◽  
Sanjeev Jain
Keyword(s):  
Thermal Comfort ◽  
Cooling System ◽  
Evaporative Cooling ◽  
Individual Performance ◽  
Coefficient Of Performance ◽  
Evaporative Cooling System ◽  
The One ◽  
Air Conditioning Systems ◽  
Tropical Climates ◽  
The Impact

The technical and economic attractiveness of a solid desiccant based evaporative cooling system depend on several factors: Configuration of the system components and their individual performance, availability of cheap but reliable regeneration heat source. In the tropical and subtropical regions, the air conditioning systems are expected to address not only the sensible loads but also, and most importantly—the loads due to higher outside humidity levels that can severely affect the thermal comfort of the building occupants. This paper reports on the dehumidification potentials of solid desiccant based evaporative cooling systems with an enthalpy exchanger operating in subtropical and tropical climates. In particular, the study presents the cooling and dehumidification capabilities of the enthalpy exchanger observed through the impact of its sensible and latent effectiveness on the thermal comfort of the conditioned space. The key performance indicators are split into two groups: (1) the thermal comfort of the conditioned space, and (2) the coefficient of performance. It was found that this cooling system with enthalpy exchanger performed better than the one without enthalpy exchanger in terms of dehumidification; however, the impact depends on the climate where the system operates.

scholarly journals Desiccant cooling as an alternative to traditional air conditioners in green cooling technology

2019 ◽  
pp. 01-13
Author(s):  
Jani DB
Keyword(s):  
Air Conditioning ◽  
Energy Savings ◽  
Cooling System ◽  
Green Building ◽  
Climatic Conditions ◽  
Coefficient Of Performance ◽  
Low Grade ◽  
Vapor Compression ◽  
Cooling Technology ◽  
Air Conditioning Systems

Desiccant-based dehumidification and air conditioning systems are considered as an energy efficient alternative to traditional vapor compression based air-conditioning systems for green building cooling technology especially in tropical hot and humid ambient climates. It is a novel green cooling technology that makes use of low-grade heat for building air conditioning. It is seen that the desiccant based dehumidification and cooling can efficiently provide comfort conditions in subtropical and especially hot and humid tropical climates. The desiccant integrated novel cooling system has a significant higher coefficient of performance compared to the conventional vapor compression system resulting to substantial electrical energy savings during the summer season by use of renewable solar energy, which also resulted in to major reduction in CO2 emissions. Therefore, these results demonstrate that there is a good potential in desiccant-based dehumidification and cooling system for energy and carbon savings while carry out building air-conditioning. Through a literature review, the feasibility of the desiccant assisted air conditioning in hot and humid climatic conditions is proven and the advantages it can offer in terms energy and cost savings are underscored. Keywords: Air-conditioning; Desiccant cooling; Dehumidification; Green cooling; Thermal comfort

ANALYSIS OF COMPETING VARIANTS OF AIR CONDITIONING SYSTEMS WITHOUT AIR EXTRACTION FROM ENGINES AT THE STAGE OF PASSENGER AIRCRAFT ONBOARD SYSTEMS CONCEPTUAL DESIGN

2019 ◽  
Vol 6 (3) ◽  
pp. 80-85
Author(s):  
Denis Igorevich Smagin ◽  
Konstantin Igorevich Starostin ◽  
Roman Sergeevich Savelyev ◽  
Anatoly Anatolyevich Satin ◽  
Anastasiya Romanovna Neveshkina ◽  
...  
Keyword(s):  
Conceptual Design ◽  
Air Conditioning ◽  
Research University ◽  
Cooling System ◽  
Fuel Efficiency ◽  
Air Cooling ◽  
Moscow Aviation Institute ◽  
Air Conditioning System ◽  
Low Efficiency ◽  
Air Conditioning Systems

One of the ways to achieve safety and comfort is to improve on-board air conditioning systems.The use of air cooling machine determines the air pressure high level at the point of selection from the aircraft engine compressor. Because of the aircraft operation in different modes and especially in the modes of small gas engines, deliberately high stages of selection have to be used for ensuring proper operation of the refrigeration machine in the modes of the aircraft small gas engines. Into force of this, most modes of aircraft operation have to throttle the pressure of the selected stage of selection, which, together with the low efficiency of the air cycle cooling system, makes the currently used air conditioning systems energy inefficient.A key feature of the architecture without air extraction from the main engines compressors is the use of electric drive compressors as a source of compressed air.A comparative analysis of competing variants of on-board air conditioning system without air extraction from engines for longrange aircraft projects was performed at the Moscow Aviation Institute (National Research University).The article deals with the main approaches to the decision-making process on the appearance of a promising aircraft on-board air conditioning system at the stage of its conceptual design and formulated the basic requirements for the structure of a complex criterion at different life cycle stages.The level of technical and technological risk, together with a larger installation weight, will require significant costs for development, testing, debugging and subsequent implementation, but at the same time on-board air conditioning system scheme without air extraction from the engines will achieve a significant increase in fuel efficiency at the level of the entire aircraft.

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