scholarly journals Mathematical Modelling of Active Magnetic Regenerator Refrigeration System for Design Considerations

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6301
Author(s):  
Aref Effatpisheh ◽  
Amir Vadiee ◽  
Behzad A. Monfared
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Single Layer ◽  
Cooling Capacity ◽  
Magnetic Refrigeration ◽  
Maximum Pressure ◽  
Refrigeration System ◽  
Design Considerations ◽  
Active Magnetic Regenerator

A magnetic refrigeration system has the potential to alternate the compression system with respect to environmental compatibility. Refrigeration systems currently operate on the basis of the expansion and compression processes, while active magnetic refrigeration systems operate based on the magnetocaloric effect. In this study, a single layer of Gd was used as the magnetocaloric material for six-packed-sphere regenerators. A one-dimensional numerical model was utilized to simulate the magnetic refrigeration system and determine the optimum parameters. The optimum mass flow rate and maximum cooling capacity at frequency of 4 Hz are 3 L·min−1 and 580 W, respectively. The results show that the maximum pressure drop increased by 1400 W at a frequency of 4 Hz and mass flow rate of 5 L·min−1. In this study, we consider the refrigeration system in terms of the design considerations, conduct a parametric study, and determine the effect of various parameters on the performance of the system.

Experimental Investigation of a Pilot Compression Chiller With Alternatives Refrigerants R401a and R134a

2005 ◽  
Author(s):  
M. Fatouh
Keyword(s):  
Experimental Investigation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Water Mass ◽  
Cooling Water ◽  
Cooling Capacity ◽  
Inlet Temperature ◽  
Chilled Water ◽  
Water Mass Flow Rate

This paper reports the results of an experimental investigation on a pilot compression chiller (4 kW cooling capacity) working with R401a and R134a as R12 alternatives. Experiments are conducted on a single-stage vapor compression refrigeration system using water as a secondary working fluid through both evaporator and condenser. Influences of cooling water mass flow rate (170–1900 kg/h), cooling water inlet temperature (27–43°C) and chilled water mass flow rate (240–1150 kg/h) on performance characteristics of chillers are evaluated for R401a, R134a and R12. Increasing cooling water mass flow rate or decreasing its inlet temperature causes the operating pressures and electric input power to reduce while the cooling capacity and coefficient of performance (COP) to increase. Pressure ratio is inversely proportional while actual loads and COP are directly proportional to chilled water mass flow rate. The effect of cooling water inlet temperature, on the system performance, is more significant than the effects of cooling and chilled water mass flow rates. Comparison between R12, R134a and R401a under identical operating conditions revealed that R401a can be used as a drop-in refrigerant to replace R12 in water-cooled chillers.

Research on Two-Phase Flow Instability in Evaporator of Refrigeration System

2010 ◽  
Author(s):  
Nan Liang ◽  
Changqing Tian ◽  
Shuangquan Shao
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Density Wave ◽  
Phase Flow ◽  
Constant Mass ◽  
Refrigeration System ◽  
Two Phase

As one kind of fluid machinery related to the two-phase flow, the refrigeration system encounters more problems of instability. It is essential to ensure the stability of the refrigeration systems for the operation and efficiency. This paper presents the experimental investigation on the static and dynamic instability in an evaporator of refrigeration system. The static instability experiments showed that the oscillatory period and swing of the mixture-vapor transition point by observation with a camera through the transparent quartz glass tube at the outlet of the evaporator. The pressure drop versus mass flow rate curves of refrigerant two phase flow in the evaporator were obtained with a negative slope region in addition to two positive slope regions, thus making the flow rate a multi-valued function of the pressure drop. For dynamic instabilities in the evaporation process, three types of oscillations (density wave type, pressure drop type and thermal type) were observed at different mass flow rates and heat fluxes, which can be represented in the pressure drop versus mass flow rate curves. For the dynamic instabilities, density wave oscillations happen when the heat flux is high with the constant mass flow rate. Thermal oscillations happen when the heat flux is correspondingly low with constant mass flow rate. Though the refrigeration system do not have special tank, the accumulator and receiver provide enough compressible volume to induce the pressure drop oscillations. The representation and characteristic of each oscillation type were also analyzed in the paper.

Micropump With Six Vibrating Membranes: Design Analysis

2008 ◽  
Author(s):  
Kittisak Koombua ◽  
Ramana M. Pidaparti ◽  
P. Worth Longest ◽  
Gary M. Atkinson
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Head ◽  
Maximum Pressure ◽  
Operating Cycle ◽  
Average Mass ◽  
Volume Method ◽  
Novel Design ◽  
Membrane Displacement

In this study, a novel design of multiple vibrating membrane micropump has been investigated. The micropump is composed of six membranes and three nozzle/diffuser elements. The membranes were vibrated out-of-phase simultaneously to create pressure difference in the pump chamber. The characteristics of this micropump were analyzed using the finite volume method. The commercial computational fluid dynamics software, FLUENT, with the dynamic mesh algorithm was employed to study velocity field and flow rate during the operating cycle. The simulation results showed that the movement of these membranes combined with the rectification behavior of three nozzle/diffuser elements can minimize back flow and improve net flow in one direction. The average mass flow rate from the micropump increased when the maximum membrane displacement and membrane frequency increased. However, the average mass flow rate from the micropump decreased when pressure head increased. Increases in maximum pressure head were associated with increases in membrane frequency.

Design and Optimization of the Restrictor of a Race Car

2015 ◽  
Author(s):  
Prithvi Raj Kokkula ◽  
Shashank Bhojappa ◽  
Selin Arslan ◽  
Badih A. Jawad
Keyword(s):  
Fluid Dynamics ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Air Flow ◽  
Intake Manifold ◽  
Maximum Pressure ◽  
Cross Sectional ◽  
Formula Sae

Formula SAE is a student competition organized by SAE International. The team of students design, manufacture and race a car. Restrictions are imposed by the Formula SAE rules committee to restrict the air flow into the intake manifold by putting a single restrictor of 20 mm. This rule limits the maximum engine power by reducing the mass flow rate flowing to the engine. The pull is greater at higher rpms and the pressure created inside the cylinder is low. As the diameter of the flow path is reduced, the cross sectional area for flow reduces. For cars running at low rpm when the engine requires less air, the reduction in area is compensated by accelerated flow of air through the restrictor. Since this is for racing purpose cars here are designed to run at very high rpms where the flow at the throat section reach sonic velocities. Due to these restrictions the teams are challenged to come up with improved restrictor designs that allow maximum pressure drop across the restrictor’s inlet and outlet. The design considered for optimizing a flow restrictor is a venturi type having 20 mm restriction between the inlet and the outlet complying with the rules set by Formula SAE committee. The primary objective of this work is to optimize the flow restriction device that achieves maximum mass flow and minimum pull from the engine. This implies the pressure difference created due to the cylinder pressure and the atmospheric pressure at the inlet should be minimum. An optimum flow restrictor is designed by conducting analysis on various converging and diverging angles and coming up with an optimum value. Venturi type is a tubular pipe with varying diameter along its length, through which the fluid flows. Law of governing fluid dynamics states that the “Velocity of the fluid increases as it passes through the constriction to satisfy the principle of continuity”. An equation can be derived from the combination of Bernoulli’s equation and Continuity equation for the pressure drop due to venturi effect. [1]. A Computational Fluid Dynamics (CFD) tool is used to calculate the minimum pressure drop across the restrictor by running a series of analysis on various converging and diverging angles and calculating the pressure drop. As a result, an optimum air flow restrictor is achieved that maximizes the mass flow rate and minimizes the engine pull.

scholarly journals Impacts of Room Temperature on the Performance of a Portable Propane Air Conditioner

2015 ◽  
Vol 23 (02) ◽  
pp. 1550015 ◽  
Author(s):  
Ahmad Sharifian ◽  
Jeri Tangalajuk Siang
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Room Temperature ◽  
Capillary Tube ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Air Conditioner ◽  
Charge Condition ◽  
Full Charge

The performance of a portable propane air conditioner system, in which the temperatures of the air passing over the condenser and evaporator are equal, has been experimentally investigated under different room temperatures and refrigerant charge levels. The research has been carried out in a range of room temperatures from 20°C to 35°C and in undercharge, standard charge and overcharge conditions. The results show that, at higher room temperatures, the refrigerant temperature in all parts of the system, the density of the refrigerant at the inlet and outlet of the condenser, mass of the refrigerant in the compressor, the mass flow rate of the refrigerant and the cooling capacity of the system in either the undercharge or full charge condition, the specific cooling capacity of the undercharge system, the useful work of the compressor, and the maximum pressure of the refrigerant increase. The increase in room temperature decreases the density of the refrigerant at the inlet and outlet of the capillary tube, the mass of the refrigerant in the capillary tube, the refrigerant subcooling at the inlet of the capillary tube, the maximum velocity of the refrigerant and the coefficient of performance. In addition, the increase in room temperature at overcharge condition causes an increase in the mass flow rate, cooling capacity and specific cooling capacity to a maximum value followed by their decrease. The most important difference between a portable air conditioner and a nonportable system is the increase in cooling capacity with an increase in room temperature in full charge condition.

A Study on Anasysis and Fabrication of an Ice Plant Model

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
J. P. Yadav ◽  
Bharat Raj Singh
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Unit Mass ◽  
Ice Plant ◽  
Plant Model ◽  
Compression Cycle ◽  
Vapour Compression

Refrigeration may be defined as the process of achieving and maintaining a temperature below that of the surroundings, the aim being to freeze ice, cool some product, or space to the required temperature. The basis of modern refrigeration is the ability of liquids to absorb enormous quantities of heat as they boil and evaporate. One of the important applications of refrigeration is in ice plant. Ice plant is used for producing refrigeration effect to freeze potable water in standard cans placed in rectangular tank which is filled by brine. Our project based on simple refrigeration system which uses the vapour compression cycle. The vapour compression cycle comprises four process compression, condensing, and expansion and evaporation process. Our ice plant model contains various parts such as- Compressor, condenser, filter drier, Expansion valve, Evaporator coil, chilling tank and various measuring equipments like digital temperature indicator, pressure gauges, energy meter etc. The conventional ice plant has been studied and a prototype model of an ice plant has been fabricated with above said accessories. The model is analyzed for its cooling capacity assumed per unit mass flow rate of refrigerant. Its COP is also calculated. The model is compared for its coefficient of performance (COP) and cooling capacity by using R-134 a refrigerant with a theoretical COP and cooling capacity obtained using refrigerant R-22. The variations found in COP and cooling capacity are 0.12 and 0.042 TR respectively for unit mass flow rate of the refrigerant.

Prediction of Performance Equations for Household Compressors Depending on Manufacturing Data for Refrigerators and Freezers

2016 ◽  
Vol 818 ◽  
pp. 184-209
Author(s):  
Louay Abdalazez Mahdi ◽  
Emad Esmaael Habib ◽  
Laith Abdalmunam
Keyword(s):  
Power Consumption ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Cooling Capacity ◽  
Surface Fitting ◽  
Temperature Cycle ◽  
Evaporator Temperature ◽  
Base Points ◽  
Swept Volume

A semi-empirical model has been investigated to represent household compressors. The model based on calorimeter data for two distinguished brand (Danfoss and Electrolux CUBIGEL) and compared with eight brands consisting of ninety compressors model. The calorimeter data are correlated (according to ARI standard 540-90 [1] and working refrigeration temperature cycle for ASHRAE Technical Committee 8.9[2]) as a function of refrigerant saturated evaporating temperatures from (-35 to 10) °C and swept volume range (2.24-11.15) cm3 keeping of the refrigerant saturated condensing temperature constant at 54.5 °C. The correlations were found with ten-coefficient polynomial by using Matlab software – surface fitting method for cooling capacity, power consumption, and refrigerant mass flow rate.In addition, other equations for cooling capacity, power consumption, and refrigerant mass flow rate at-23.3 °C evaporator temperature, 54.4 °C condenser temperature, and 32 °C temperature for liquid line which is the base points of the refrigerator cycle according to ASHRAE[2] , cover the range (2.42-11.15) cm3 swept volume which are created to quick choose the proper compressor.The result indicated that the surface fitting models are accurate within ± 15% deviation of compressors data of seventy-two models for cooling capacity, fifty models for power, and twenty-five models for refrigerant mass flow rate.

Performance Evaluation of Concentrated Photovoltaic System Using a Microchannel Heat Sink

2016 ◽  
Author(s):  
Ali Radwan ◽  
Mahmoud Ahmed ◽  
Shinichi Ookawara
Keyword(s):  
Solar Cell ◽  
Mass Flow Rate ◽  
Double Layer ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Sink ◽  
Single Layer ◽  
Microchannel Heat Sink ◽  
Pumping Power ◽  
Cell Temperature

The high incident heat flux on the concentrated photovoltaic (CPV) system causes a significant increase in the cell temperature and thus reduces the system efficiency. Therefore, using an efficient cooling technique is of great importance for those systems. In the present study, a new technology for concentrated photovoltaic systems is introduced using a truncated-double layer microchannel heat sink. A comprehensive three-dimensional thermo-fluid model for the photovoltaic layers integrated with a microchannel heat sink was developed. The proposed model was simulated numerically to estimate the solar cell temperature, temperature uniformity, cooling system pumping power, electrical efficiency and thermal efficiency of the CPV system. The numerical results were validated with the available experimental, analytical and numerical results in the literature. In the designed heat sink, various design parameters are investigated such as the truncation length, cooling mass flow rate, concentration ratio, and converging width ratio of the flow channel. Results indicate that increasing the truncated length leads to an increase of solar cell temperature at a constant coolant mass flow rate. The cell temperature varies between 80.1°C and 146.5°C as the truncation length ratio increases from 0 (i.e. single layer microchannel) to 1 respectively at a concentration ratio (CR) of 40 and a cooling mass flow rate (ṁ) of 26.6 g/min. Using the double layer microchannel reduces the consumed pumping power at the same total mass flow rate compared to the single layer microchannel. The Double layer configuration with a truncation length ratio (l/lsc) equal to unity achieves a lower pumping power and solar cell temperature uniformity in comparison to the single layer microchannel.

Experimental study of an ultrasonic regenerative evaporative cooler for a desiccant cooling system

2018 ◽  
Vol 40 (2) ◽  
pp. 151-175 ◽  
Author(s):  
BS Arun ◽  
V Mariappan
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Cooling System ◽  
Cooling Capacity ◽  
Water Mist ◽  
Extraction Ratio ◽  
Feed Water ◽  
Airflow Rate ◽  
Evaporative Cooler

This paper presents fabrication of an ultrasonic regenerative evaporative cooler, coupled with a desiccant dehumidifier. Ultrasonic regenerative evaporative cooler consists of several sets of a dry channel and a wet channel. A part of the air from the dry channel is redirected into the wet channel where it is cooled by evaporation of water mist from an ultrasonic atomiser. Air flowing through dry channels is pre-cooled by heat transfer between wet and dry channels, without changing its humidity. In this cooler, the conventional hygroscopic layer for wetting the plate surface is replaced with the water mist. It is observed that the performance of the cooling system significantly depends on the channel spacing, channel length, inlet airflow rate and extraction ratio, and marginally depends upon feed water temperature. The room cooling capacity is eminently responsive to both air mass flow rate and extraction ratio. The maximum available room cooling capacity of 339.8 W is obtained for the optimal values of 0.0488 kg/s mass flow rate of air and 0.37 extraction ratio. The prototype achieved wet-bulb effectiveness values as high as 1.15 and delivered more than 10℃ temperature drop. Practical application: An ultrasonic regenerative evaporative cooler can be coupled with a desiccant dehumidification unit for use in hot and humid climate to achieve comfort condition utilising less energy and feed water when compared to the vapour compression refrigeration system. From this prototype researchers and engineers can develop, by combining desiccant regenerators and evaporative coolers which use ultrasonic method for low-temperature dehydration of desiccant substance. Solar thermal energy can also be directly utilised for marginally heating the desiccant substance during the regeneration process. Overall, this system can contribute to the development of energy efficient buildings.

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