Experimental analysis of an improved Maisotsenko cycle design under low velocity conditions (original) (raw)
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Energy, 2014
In this paper a novel cross-flow HMX (heat and mass exchanger) utilizing the M-cycle (Maisotsenko cycle) for dew point indirect evaporative cooling has been tested for the performance evaluation in terms of thermal effectiveness and specific cooling capacity under various ambient and operational conditions. Additionally, the operational performance of the investigated HMX was examined on the base of developed model. The obtained results from the model prediction have been compared with the experimental data. The positive results of this validation indicated that the proposed model may be successfully used for prediction of operational performance of the investigated HMX. The analysis presented in this paper further demonstrates attractiveness and high efficiency of the novel M-cycle HMX used for indirect evaporative cooling in air conditioning units.
PARAMETRIC INVESTIGATION OF A COUNTER-FLOW HEAT AND MASS EXCHANGER BASED ON MAISOTSENKO CYCLE
The performance of a dew-point cooler is analyzed in terms of various parameters including dew point and wet bulb effectiveness. An experimental setup of a counter-flow heat and mass exchanger [HMX] based on Maisotsenko cycle (M-cycle) evaporation technique is established. The setup consists of 8 dry channels made of Aluminum sheets and 7 wet channels made of kraft paper. Experimental analysis is performed under wide range of operating parameters including air absolute humidity i.e. 12.7 g/kg to 18g/kg, air temperature i.e. 20 to 55oC, and inlet velocities i.e. 0.88 to 1.50 m/s. The results indicate that appreciably higher value of dew-point and the wet-bulb effectiveness can be achieved ranging up to a maximum of 93% and to 130%, respectively at various inlet air conditions. Apart from the ambient air conditions, influence of amount of air diversion to wet side of channel is also studied. It is observed that this design feature of HMX can lead to a substantial increase of dew-point and wet-bulb effectiveness. By varying the inlet to wet side air ratio, a suitable limit of the quantity of inlet air diversion to working side is also suggested.
A Review on Potential of Indirect Evaporative Cooling System
One of the world's most energy consuming sector is heating, ventilation and air conditioning. A lot of energy is consumed by traditional cooling systems based on the conventional vapour compression refrigeration cycle. The VCR system which contains refrigerants in circuits produced a harmful effect on environment and also dangerous to human life if leakages occur. These factors were mainly responsible for the development of evaporative coolers. In direct evaporative cooling system, it will give adequate temperature drop of air with increase in humidity which is not desirable for human health. So for overcoming these difficulties, indirect evaporative cooling system will be used for air coolers in which heat mass exchanger is used. To get higher temperature drop and wet bulb effectiveness above 100%, Scientist Valeriy Maisotsenko developed Maisotsenko cycle. The aim of our study is to find the best alternative of existing conventional cooling systems.
Numerical study of a M-cycle cross-flow heat exchanger for indirect evaporative cooling
Building and Environment, 2011
In this paper, numerical analyses of the thermal performance of an indirect evaporative air cooler incorporating a M-cycle cross-flow heat exchanger has been carried out. The numerical model was established from solving the coupled governing equations for heat and mass transfer between the product and working air, using the finite-element method. The model was developed using the EES (Engineering Equation Solver) environment and validated by published experimental data. Correlation between the cooling (wet-bulb) effectiveness, system COP and a number of air flow/exchanger parameters was developed. It is found that lower channel air velocity, lower inlet air relative humidity, and higher working-to-product air ratio yielded higher cooling effectiveness. The recommended average air velocities in dry and wet channels should not be greater than 1.77 m/s and 0.7 m/s, respectively. The optimum flow ratio of working-to-product air for this cooler is 50%. The channel geometric sizes, i.e. channel length and height, also impose significant impact to system performance. Longer channel length and smaller channel height contribute to increase of the system cooling effectiveness but lead to reduced system COP. The recommend channel height is 4 mm and the dimensionless channel length, i.e., ratio of the channel length to height, should be in the range 100 to 300. Numerical study results indicated that this new type of M-cycle heat and mass exchanger can achieve 16.7% higher cooling effectiveness compared with the conventional cross-flow heat and mass exchanger for the indirect evaporative cooler. The model of this kind is new and not yet reported in literatures. The results of the study help with design and performance analyses of such a new type of indirect evaporative air cooler, and in further, help increasing market rating of the technology within building air conditioning sector, which is currently dominated by the conventional compression refrigeration technology.
International Journal of Low-Carbon Technologies
This paper aimed to numerically investigate the performance comparison between counterflow and crossflow heat exchangers for indirect evaporative air cooler. Simulation results indicate that cooling performance difference between the two configurations considerably depends on the configuration structure of heat exchangers, the inlet air status and the mass flow rates of primary and secondary. Among types of the cross-sectional shape considered in this paper, the counter configuration with rectangle channels which has a length-to-width ratio of 16:1 can provide the best cooling performance. The wet bulb effectiveness of counterflow configuration is about 7% greater than that of crossflow configuration with increasing inlet air temperature on average. The higher the inlet air temperature, the bigger the EER, cooling capacity and supply air temperature difference between the two configurations. With increasing relative humidity, the two configurations keep an average wet bulb effective...
Energy Conversion and Management, 2015
This report describes numerical modelling of heat and mass transfer in exchangers utilizing the Maisotsenko Cycle for indirect evaporative cooling. For this purpose, numerical models are developed based on the modified ε-NTU method to perform thermal calculations of the indirect evaporative cooling process, thus quantifying overall performance of considered heat exchangers. Numerical simulation reveals many unique features of considered HMX (heat and mass exchanger), enabling an accurate prediction of its performance. The results of computer simulation showed high efficiency gains that are sensitive to various inlet conditions, and allow for estimation of optimum operating conditions, including suitable climatic zones for the proposed unit using.
Engineering Applications of Computational Fluid Mechanics , 2020
In this work, a numerical and experimental study is performed to evaluate the affecting variables on energy efficiency of a novel regenerative evaporative cooler utilizing dew-point indirect evaporative cooling. For first time, an investigation is experimentally and numerically carried out to study the effects of the channel number on important parameters such as product temperature and humidity ratio. Investigations are carried out for five configurations with various channel numbers. The comparison of the numerical and experimental results is obtained and well accuracy observed. For the five studied configurations, the results show that with an increase in the number of channels, the outlet temperature decreases. For an inlet air flow rate of 100–600m3/h, the cooled outlet flow temperature changes to the range of 23.4–30.7°C, 19.7–28.3°C, 18–26.4°C, 17.2–25°C and 16.6–23.8°C. For the configurations with finned channels, the percentage of increase in produced air temperature reaches 11.5% for HMX B, 18.6% for HMX C, 23.4% for HMX D and 26.9% for HMX E, as compared with HMX A.
Theoretical study of the basic cycles for indirect evaporative air cooling
International Journal of Heat and Mass Transfer, 2015
This paper presents a numerical study of heat and mass transfer in indirect evaporative air coolers with four air flow patterns: parallel-flow, counter-flow, cross-flow and regenerative. The numerical simulation was performed on the basis of original two-dimensional heat and mass transfer models (in the case of cross-flow heat exchanger the model was 3D). The mathematical models developed were validated against published experimental data presented in Appendix A. It was established, that heat and mass transfer processes in the wet channels of counter-flow, cross-flow and regenerative indirect evaporative coolers are characterized by creation of two particular heat and mass transfer zones. Detail analysis of the temperature and humidity ratio distributions and boundary conditions, characterizing the coupled heat and mass transfer process in each of these determined zones, revels the violation of the Lewis relation unity under a certain inlet and operation conditions. A theoretical method for estimating the Lewis factor was proposed. Using the developed models the thermal performances of the conventional designs of indirect evaporative air coolers were analyzed numerically and preferable climatic zones for considered heat exchanger were established. Four novel heat exchangers utilizing the advantages of the basic cycles heat exchangers were presented.
Frontiers in Mechanical Engineering, 2022
The satisfactory performance of indirect evaporative cooling techniques (IEC) is governed significantly by the structural and design arrangement of heat and mass exchange devices. The experimental performance of the dew point evaporative cooler has been investigated in the present work with the geometrically modified flow passages for air and water. Conventionally, these passages are formed by either flat or corrugated plates. The trapezoidal corrugated plate has been used to form these passages for air and water. The laboratory trials were conducted for the different combinations of intake air temperature, specific humidity, and air velocity. The performance in terms of dew point and wet bulb efficiency is presented based on laboratory trials. The experimental results achieved dew point and wet bulb efficiencies ranging between 52% and 82% and 74% and 126%, respectively. The geometrically modified flow passages increase the heat exchange area for the same volume of a similar heat exchange device and achieve an increased thermal performance of the proposed cooler.
Energy, 2011
This paper provides a comparative study of the performance of cross-flow and counter-flow M-cycle heat exchangers for dew point cooling. It is recognised that evaporative cooling systems offer a low energy alternative to conventional air conditioning units. Recently emerged dew point cooling, as the renovated evaporative cooling configuration, is claimed to have much higher cooling output over the conventional evaporative modes owing to use of the M-cycle heat exchangers. Cross-flow and counter-flow heat exchangers, as the available structures for M-cycle dew point cooling processing, were theoretically and experimentally investigated to identify the difference in cooling effectiveness of both under the parallel structural/operational conditions, optimise the geometrical sizes of the exchangers and suggest their favourite operational conditions. Through development of a dedicated computer model and case-by-case experimental testing and validation, a parametric study of the cooling performance of the counter-flow and cross-flow heat exchangers was carried out. The results showed the counter-flow exchanger offered greater (around 20% higher) cooling capacity, as well as greater (15%e23% higher) dew-point and wet-bulb effectiveness when equal in physical size and under the same operating conditions. The crossflow system, however, had a greater (10% higher) Energy Efficiency (COP). As the increased cooling effectiveness will lead to reduced air volume flow rate, smaller system size and lower cost, whilst the size and cost are the inherent barriers for use of dew point cooling as the alternation of the conventional cooling systems, the counter-flow system is considered to offer practical advantages over the cross-flow system that would aid the uptake of this low energy cooling alternative. In line with increased global demand for energy in cooling of building, largely by economic booming of emerging developing nations and recognised global warming, the research results will be of significant importance in terms of promoting deployment of the low energy dew point cooling system, helping reduction of energy use in cooling of buildings and cut of the associated carbon emission.