Conventional Coolers Research Articles

Daytime radiative cooling using pattern free metal dielectric coating

Radiative coolers, which dumps the excess heat to the cold outer space by releasing the thermal radiation through the atmospheric window, have offered an alternate and feasible solution to the conventional coolers that are fueled on the electricity produced by either using renewal or non-renewal sources like fossil fuels. Particularly, daytime passive radiative coolers have paved the way for many energy free technology that are used in reducing the temperature of building tops, power plants, and water harvesting. In this, we propose a pattern free and large area scalable bi-layered thin film based daytime radiative cooler. The proposed design illustrates an average reflectivity of 98.5% for the solar spectrum, while showing average emittance of 91% within the atmospheric window (8-13μm). The design consists of thin films of transparent dielectrics such as ZnS or BaF2 placed on top of a thick glass substrate, that is backed by a thin film silver. We theoretically obtained a cooling power of 119 W.m−2 with a temperature reduction of 9 °C below the ambient.

Testing the Impact of Vibration on Changes in the Number of Erythrocytes and Platelet Counts in Whole Blood

Blood or plasma is transferred from the unit car to the Blood Donor Unit using a conventional cooler box without any tools to maintain the effect of vibration which is very possible for a decrease in blood quality. Examination carried out to determine the quality of blood through routine hematological examination by counting the number of erythrocytes and platelets. The purpose of this study was to determine the impact of vibration on the number of red blood cells and thrombocytes. The research design was a pre and post test with control group design. The sample size for each group was nine tubes of blood. Data was processed by one way ANOVA and tukeys HSD test. Results There was a significant difference in the number of erythrocytes between the group that was vibrated at a frequency of 11 HZ compared to the group that was vibrated at a frequency of 0 HZ and 5 HZ with p values 0.00 and 0.01, respectively. There was a significant difference in the number of platelets between the groups that were vibrated with a frequency of 11 HZ compared to the groups that were vibrated with a frequency of 0 HZ and 5 HZ with a p value of 0.00. It was concluded that vibrations exceeding 10 Hz could decrease the number of erythrocytes and platelets in whole blood

Testing the Impact of Vibration on Changes in the Number of Erythrocytes and Platelet Counts in Whole Blood

Blood or plasma is transferred from the unit car to the Blood Donor Unit using a conventional cooler box without any tools to maintain the effect of vibration which is very possible for a decrease in blood quality. Examination carried out to determine the quality of blood through routine hematological examination by counting the number of erythrocytes and platelets. The purpose of this study was to determine the impact of vibration on the number of red blood cells and thrombocytes. The research design was a pre and post test with control group design. The sample size for each group was nine tubes of blood. Data was processed by one way ANOVA and tukeys HSD test. Results There was a significant difference in the number of erythrocytes between the group that was vibrated at a frequency of 11 HZ compared to the group that was vibrated at a frequency of 0 HZ and 5 HZ with p values 0.00 and 0.01, respectively. There was a significant difference in the number of platelets between the groups that were vibrated with a frequency of 11 HZ compared to the groups that were vibrated with a frequency of 0 HZ and 5 HZ with a p value of 0.00. It was concluded that vibrations exceeding 10 Hz could decrease the number of erythrocytes and platelets in whole blood

Enhancement of the cooling by mixed convection of a CPU using a rotating heat sink: Numerical study

The technological progress made in recent years has driven electronic apparatus to become not only more efficient and work faster but also considerably smaller in weight and size. Furthermore, the power densities of these devices have known an impressive increase. However, the challenge for the electronic industry is the lifetime device improvement by controlling the adequate removal of their excess heat. The use of more efficient cooling systems is, therefore, crucial in order to ensure durable device functionality. In this work, computational simulation was carried out to study the enhancement cooling process mixed convection of an electronic component (CPU mounted in a motherboard) using a new design of a heat exchanger by combining the heat sink (the finned surface) and the fan in a single component, this allows more heat to be moved faster and with less energy than a conventional cooler. Three radial heat sinks (HS18, HS24 and HS36) are considered depending on circumferential fin numbers ( n = 18, 24 and 36). The effect of Reynolds number, heat flux and rotational velocity is investigated, and the optimum comprehensive performance was determined. The results reveal the cooling performance turns out to be better for heat sink with n = 36. The rotational velocity operates a significant effect on the temperature field only for values below than 900 rpm. We also found that the improvement in the Nusselt number and its percentage enhancement is intensified with increased rotational velocity and decreased with heat flux. A bigger Ω and ReΩ meant a more obvious heat transfer enhancement (NuΩ/Nu0) in the case of smaller Q, but (NuΩ/Nu0) decreased with increasing Q.

Design and Fabrication of Refrigerant Based Air Cooler

Abstract: With the recent government organization and regulation for saving the water, trees, curtains to the use of these sources which contribute to global warming present day mankind uses various equipment in their daily need which includes conventional cooler, AC etc. This consumes large amount of water and electricity so for reducing the use of these main sources research involves the use of VCRS system which include eco-friendly refrigerant R134a in cooler system. This system is mounted in the research model in a proper manner so that it is compact in size. The refrigerant R134a absorbs the heat from air and makes the air cooled, itself getting vaporized in evaporator and then the cooled air is sent outward from the opening. In the research model with help of fan running on motor and gives the cooling effect. This use of VCRS system with eco -friendly refrigerant reduces the consumption of the water, electricity consumption and tree which is used for making wood wool in conventional cooler. This ultimately reduces the global warming. For making these purposes the project is developed. Keywords: Compressor, condenser, evaporator, refrigerant(R134a), expansion device

Literature Review on Design and Fabrication of Refrigerant Based Air Cooler

Abstract: With the recent government organization and regulation for saving the water, trees, curtains to the use of these sources which contribute to global warming present day mankind uses various equipment in their daily need which includes conventional cooler, AC etc. This consumes large amount of water and electricity so for reducing the use of these main sources research involves the use of VCRS system which include eco-friendly refrigerant R134a in cooler system. This system is mounted in the research model in a proper manner so that it is compact in size. The refrigerant R134a absorbs the heat from air and makes the air cooled, itself getting vaporized in evaporator and then the cooled air is sent outward from the opening. In the research model with help of fan running on motor and gives the cooling effect. This use of VCRS system with eco -friendly refrigerant reduces the consumption of the water, electricity consumption and tree which is used for making wood wool in conventional cooler. This ultimately reduces the global warming. For making these purposes the project is developed. Keywords: Compressor, condenser, evaporator, refrigerant(R134a), expansion device

A Dual‐Mode Infrared Asymmetric Photonic Structure for All‐Season Passive Radiative Cooling and Heating

AbstractRadiative cooling is a revolutionary sustainable thermoregulating technology in favor to fight against global warming and urban heat island effects. However, the conventional designed high infrared emissive coolers do not function satisfactorily under atmospheric counter radiation (cloudy, humid, reduced sky access conditions) nor for all‐season thermal requirement (cooling and/or heating). Dual‐mode asymmetric photonic mirror (APM) consisted of silicon‐based diffractive gratings is presented, approaching an all‐season and all‐terrain optimized radiative thermal regulation. Based on the mechanism of asymmetric diffraction through high refractive index contrast mediums, the designed APM establishes an asymmetric radiative heat transfer channel for cooling and heating. An average infrared asymmetry of 20% for outgoing and incoming radiation is achieved by the fabricated APM. The remarkable cooling power of APM surpasses 80% over the standalone radiative cooler (RC) for counter radiation conditions. Under cloudy sky, the cooling‐APM achieves 8 °C lower than RC standalone, while the heating‐APM 5.7 °C higher, which presents prominent advantages over conventional coolers for different thermal management needs. The proposed dual‐mode infrared asymmetric photonic structure is promising to overcome shortcomings of conventional radiative cooling and offers breakthrough developments in future energy‐saving thermal management system.

Effects of Humidity Pretreatment Devices on the Loss of HCl Gas Emitted from Industrial Stacks

A high humidity at a high temperature presents a common challenge in monitoring the air pollutants emitted from stationary sources. Thus, humidity removal is a pivotal issue. In this study, the effect of humidity pretreatment devices (HPDs) on hydrogen chloride (HCl) gas emitted from an incinerator stack was investigated. A conventional cooler (HPD_CL), and poly-tube (HPD_NP) and single-tube (HPD_NS) Nafion™ dryers were used as HPDs in this study. HCl concentrations varied at five and 10 parts per million in volume (ppmv). Low (i.e., ~4%) and high (i.e., ~17%) humidities were generated at 180 °C. The removal efficiencies of humidity and the loss rates of HCl by the devices were determined. The removal efficiencies of humidity by HPD_CL and the two dryers were found to be similar, at approximately 85% at a low humidity and 95% at a high humidity. In terms of HCl loss rates, HPD_CL revealed the highest loss rates in all conditions (i.e., >95%), followed by HPD_NP and HPD_NS. At normal room temperature (i.e., 25 °C), the HCl loss rates of HPD_NP were >40% at a low humidity and >70% at a high humidity, while those of HPD_NS were >10% at a low humidity and >60% at a high humidity. The performance of the two dryers improved when they were heated to 80 °C. However, this temperature caused damage to the dryers, which reduced their lifetime.

Modeling Efficient Hybrid Air Conditioning System

The main objective of the present study is to investigate the thermal performance of the air chiller using the heat exchanger using the chilled water tank by Freon R-134a. The air chiller model was designed and fabricated with all measuring devices in the AL-Muthanna city environment. The practical tests were carried out with a change in the factors governing air coolant performance to investigate their effects on the properties of the system. The study covered the values of the cooling water flow rate at (2l/min) and the evaporator water temperature (2.5 to 5.69 °C) and the return water temperature in the reservoir ranged from 11.6 to 19.2 °C). The greatest coefficient of thermal performance in the system was (5) while the lowest coefficient of thermal performance was (3.6) and that agreement to the experimental studies of this type of system. The results showed that the average guidance in the consumption of air-chilled energy by using the water tank and Freon R-134a was about 13% to 32% compared to the conventional air conditioner. All through the results indicated that the addition of a cooling stage to the conventional cooler inside the testing room results in lowering the temperature (dry temperature) by (27%) and reduced the relative humidity by (36%).

Performance Enhancement of Spaceborne Cooler Passive Launch and On-Orbit Vibration Isolation System

A spaceborne cryogenic cooler induces undesirable microvibration disturbances during its on-orbit operation, which is one of the main sources that degrades the image quality of submeter-level high-resolution observation satellites. Several types of vibration isolation systems based on passive approaches have been developed for reducing the microvibration of the cooler. A coil-spring-type passive vibration isolation system developed in a previous study has shown excellent performance in both launch vibration and on-orbit microvibration isolation. To improve the capability of the conventional cooler isolator, including the position sensitivity and launch vibration reduction, we propose a new version of a dual coil-spring-type passive vibration isolator system. The effectiveness of the newly proposed design was validated through a microjitter measurement test, position sensitivity test, and qualification-level launch vibration test of the isolator.

Study of the Cooling Performance of a Mist-Type Regenerative Evaporative Cooler Under Different Feed Water Temperature

In hot and humid climates, evaporative cooler is coupled with desiccant dehumidifier to obtain effective cooling. To realize the M-cycle-based cooler which combines liquid desiccant regeneration and evaporative cooling in a single apparatus, the effect of different feed water temperature on cooling performance is investigated in this paper. It was observed that wetting water film layer of conventional regenerative evaporative cooler (REC) carries a significant amount of sensible heat from the hot water/solution which reduced the wet-bulb effectiveness of the cooler. To enhance its effectiveness, an ultrasonic atomization mist REC was proposed. The influence of different intake conditions on cooling performance was studied and found that mist REC performed better than conventional cooler for higher feed water temperature. The wet-bulb effectiveness of the cooler ranged from 0.56 to 1.15 with maximum cooling capacity of 580[Formula: see text]W, which is comparable to the previous studies. This prototype can be further developed to an ultrasonic liquid desiccant waterless evaporative cooler.

Self‐Actuating Electrocaloric Cooling Fibers

AbstractSolid‐state cooling fibers comprising an electrocaloric polymer, poly(vinylidene fluoride‐trifluoroethylene‐chlorofluoroethylene) terpolymer, spray‐coated on a conductive fiber core electrode, and a coaxially coated single‐walled carbon nanotubes outer electrode are reported. The fiber coolers can be less than 160 µm thin and more than 8 cm long. Measured cooling ΔT of the EC fibers is 0.7 °C at an electric field of 100 V µm−1 applied between the electrodes. The fiber coolers are flexible; 2000 cycles of repeated bending to a 2.5 mm curvature radius do not significantly degrade the cooling ΔT. Self‐actuated bending of the fibers is observed during the EC operation, which allows the EC fibers to move heat from one location to another without any additional driving mechanisms such as electromagnetic motors, pumps, or electrostatic actuation that are commonly used in conventional coolers. The self‐actuating EC fibers represent the first ever active cooler in a thin fiber form factor.

Accurate setting of electron energy for demonstration of first hadron beam cooling with rf-accelerated electron bunches

The world's first electron cooling based on the rf acceleration of electron bunches was experimentally demonstrated at the Low Energy RHIC Electron Cooler (LEReC) at Brookhaven National Laboratory. The critical step in obtaining cooling of the Au ions in the collider with this new approach was matching the electron and ion relativistic $\ensuremath{\gamma}$-factors with a relative error of less than $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$. Since the electron beam kinetic energy was just 1.6 MeV, it was required to set the absolute energy of electrons with an accuracy better than 0.8 keV. The method of setting electron energy in conventional coolers was unsuitable for LEReC and a new technique had to be developed. In this paper we describe our experience with measuring the electron beam energy at LEReC and precisely matching electron and ion $\ensuremath{\gamma}$-factors, which resulted in demonstration of the cooling.

Artificial Perspiration Membrane by Programmed Deformation of Thermoresponsive Hydrogels.

Thermal management is essential for living organisms and electronic devices to survive and maintain their own functions. However, developing flexible cooling devices for flexible electronics or biological systems is challenging because conventional coolers are bulky and require rigid batteries. In nature, skins help to maintain a constant body temperature by dissipating heat through perspiration. Inspired by nature, an artificial perspiration membrane that automatically regulates evaporation depending on temperature using the programmed deformation of thermoresponsive hydrogels is presented. The thermoresponsive hydrogel is patterned into pinwheel shapes and supported by a polymeric rigid frame with stable adhesion using copolymerization. Both shape of the valve and mechanical constraint of the frame allow six times larger evaporation area in the open state compared to the closed state, and the transition occurs at a fast rate (≈1 s). A stretchable membrane is selectively coated to prevent unintended evaporation through the hydrogel while allowing swelling or shrinking of the hydrogel by securing path of water. Consequently, a 30% reduction in evaporation is observed at lower temperature, resulting in regulation of the skin temperature at the thermal model of human skins. This simple, small, and flexible cooler will be useful for maintaining temperature of flexible devices.

CONVERSION OF DESSERT COOLER INTO LOW COST AIR CONDITIONER USING PELTIER MODULE

This paper describes design and fabrication of dessert cooler with certain modifications so that it can be used as low cost air conditioner. The cooling in conventional cooler is done along Wet Bulb Temperature line that reduces Dry Bulb Temperature but simultaneously it increases specific humidly. This paper aims to reduce this humidity with the use of peltier module. This system provides better results than that of conventional cooler. The only disadvantage observed; is long time required to get the desired cooling effect.

Investigation of Phase Change Material as a Potential Replacement of EGR Cooler

Phase Change Materials (PCM) are used widely in passive heat storage system due to their high heat retention capacities. In the present work an attempt is made to use the PCM as an effective replacement to conventional EGR cooler. The prime advantages of using PCM as an alternative to the traditionally used EGR coolers are that, the pumping operation will no longer be a continuous process hence the power consumed by pumps would drastically reduce, so does the load on the engine and secondly there would be significant reduction in the weight of the system which would ultimately boost the fuel economy of the vehicle. The PCM candidate chosen for study is a Salt blend (59%KF+29%LiF+12%NaF). The chosen specimen's thermal performance is computed based on the duration for which the refrigerant pump remains idle. Using numerical simulation the melting period of PCM(Salt Blend) is computed and the simulation is verified by already established numerical and experimental results for a different material, Rubitherm (RT-42).

Cooling-water system optimisation with a novel two-step sequential method

In cooling water systems, conventional cooler networks usually operate in a parallel configuration and traditional pump networks consist of pumps which are installed only on the main supply pipeline. However, a series-parallel configuration of coolers can substantially increase the cooling-water return temperature and reduce its flow-rate as well as the efficiency of the cooling tower, but the pressure drop along pipes would increase correspondingly. This paper presents a novel two-step sequential methodology for the optimisation of cooling-water system (CWS). The first step is to use a thermodynamic model to obtain the optimal cooler network. In the second step, the hydraulic model is established to obtain the optimal pump network with auxiliary pumps installed in parallel branch pipes. The proposed model can identify the optimal distribution of cooling water within the network and the optimal installation locations and pressure head of pumps required for CWS. A case study is presented to demonstrate the effectiveness of the proposed methodology. It can save up to 23.3% of the cooler network cost and additional 11% of the pump network cost after optimisation.

Study on the COP of free piston Stirling cooler (FPSC) in the anti-sublimation CO2 capture process

Free piston Stirling cooler (FPSC) is a promising alternative for the conventional coolers and has been applied to various fields. In the previous research, a novel cryogenic CO2 capture system based on FPSCs has been exploited. In order to enhance the cryogenic CO2 capture efficiency, the investigation on the coefficient of performance (COP) of the FPSC is carried out in this work. In detail, the influence of different materials (aluminium and copper), size of cold head (length and diameter), as well as ambient conditions (humidity and temperature) on the COP of the cryogenic system were tested. The experiment results indicate that the material of cold head should be selected at copper to increase the COP of CO2 capture system. The length and diameter of cold head should be short and thick. In addition, the low ambient temperature is benefit for the high COP. For the optimal conditions (the material was copper, length and diameter were 180 and 40 mm, respectively), the temperature of the cold head reached −140 °C, and the COP of the FPSC and the cryogenic CO2 system was 0.82 and 0.70, respectively.

Development and performance estimation of an exhaust gas recirculation cooler with dimpled rectangular tubes

In this study, an exhaust gas recirculation (EGR) cooler with dimpled rectangular tubes, whose heat exchange effectiveness is higher than that of a conventional cooler, is developed. To maximize the heat transfer between the exhaust gas and coolant, the dimples are formed on the surface of the heat exchange tubes. A dimpled-tube manufacturing process is established that comprises: dimple shape forming, edge bending, centre v-notch bending, compression, and plasma welding. The high effectiveness of the dimple-type EGR cooler is confirmed by the effectiveness-NTU method and experimental approaches under normal operating conditions. It is also important to verify the structural integrity, in view of the practical uses of the dimple-type EGR cooler. In order to confirm the safety of the EGR cooler, finite element analyses are carried out for each component, such as the oval core tube with a dimpled shape. The structural integrity under thermal stress and pressure, which are caused by gas and coolant flows in the shell and tubes, is evaluated through thermal and structural analyses.

Solid-State Microrefrigeration in Conjunction With Liquid Cooling

Thermal design requirements are mostly driven by the peak temperatures. Reducing or eliminating hot spots could alleviate the design requirement for the whole package. Combination of solid-state and liquid cooling will allow removal of both hot spots and background heating. In this paper, we analyze the performance of thin film Bi2Te3 microcooler and the 3D SiGe-based microrefrigerator, and optimize the maximum cooling and cooling power density in the presence of a liquid flow. Liquid flow and heat transfer coefficient will change the background temperature of the chip but they also affect the performance of the solid-state coolers used to remove hot spots. Both Peltier cooling at interfaces and Joule heating inside the device could be affected by the fluid flow. We analyze conventional Peltier coolers as well as 3D coolers. We study the impact of various parameters such as thermoelectric leg thickness, thermal interface resistances, and geometry factor on the overall system performance. We find that the cooling of a conventional Peltier cooler is significantly reduced in the presence of fluid flow. On the other hand, 3D SiGe cooler can be effective to remove high power density hot spots up to 500 W/cm2. 3D microrefrigerators can have a significant impact if the thermoelectric figure-of-merit, ZT, could reach 0.5 for a material grown on silicon substrate. It is interesting to note that there is an optimum microrefrigerator active region thickness that gives the maximum localized cooling. For liquid heat transfer coefficient between 5000 and 20,000 W m−2 K−1, the optimum is found to be between 10 μm and 20 μm.