Flexible Joule-Thomson Micro-Refrigerator

2009 ◽  
Author(s):  
M. Kohno ◽  
A. Tanabe ◽  
Y. Kuwamoto ◽  
H. Kubota ◽  
Y. Takata
Keyword(s):  
Heat Exchanger ◽  
Numerical Analysis ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
Cooling Power ◽  
Temperature Profiles ◽  
Evaporator Temperature ◽  
Cooling Performance ◽  
Inner Diameter ◽  
Outside Diameter

In this study, a prototype flexible Joule-Thomson micro-refrigerator was fabricated and its cooling power was examined. The micro-refrigerator uses N2, C2H4 or CO2 as a working gas and it consists mainly of a heat exchanger and an evaporator. The outside diameter of the heat exchanger outer tube is 0.9 mm and that of the inner tube is 0.4 mm. The length of the heat exchanger is 450mm. The inner diameter of the evaporator capillary is 0.1 mm. A cooling power of 100 mW at an evaporator temperature of 277 K was attained for inlet and outlet gas (CO2) pressures of 5.0 MPa and 0.1 MPa, respectively. To understand the cooling performance, a numerical analysis of the heat exchanger has been done and the effects of mass flow rate and dimensions of the heat exchanger on temperature profiles and effectiveness were examined.

Micro-Refrigerator Fabricated on Silicon Wafer

2007 ◽  
Author(s):  
Y. Takata ◽  
K. Sugahara ◽  
T. Tachikawa ◽  
S. Moroe ◽  
H. Kubota ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Numerical Analysis ◽  
Silicon Wafer ◽  
Flow Rate ◽  
Cooling Power ◽  
Temperature Profiles ◽  
Evaporator Temperature ◽  
Cooling Performance ◽  
Gas Pressures

A prototype Joule-Thomson micro-cooler was fabricated on silicon wafer by making use of photofabrication. The micro-cooler uses ethylene as a refrigerant and it consists mainly of heat exchanger and evaporator. The cooling power of 20mW at evaporator temperature of 272K was attained at the inlet and outlet gas pressures of 2.5MPa and 0.1MPa, respectively. To understand the low cooling performance, numerical analysis of heat exchanger has been done and the effects of mass flow rate and thermal conductivity of solid on temperature profiles and effectiveness were examined. It was found that the flow rate of present experiment is too large and the decrease in flow rate gives better temperature effectiveness of heat exchanger. It was also found that the low thermal conductivity of solid improves the performance of heat exchanger.

scholarly journals Modelling an unconventional closed-loop deep borehole heat exchanger (DBHE): sensitivity analysis on the Newberry volcanic setting

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Hannah R. Doran ◽  
Theo Renaud ◽  
Gioia Falcone ◽  
Lehua Pan ◽  
Patrick G. Verdin
Keyword(s):  
Sensitivity Analysis ◽  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Energy Flow ◽  
Closed Loop ◽  
Working Fluid ◽  
Valuable Insight ◽  
Deep Borehole

AbstractAlternative (unconventional) deep geothermal designs are needed to provide a secure and efficient geothermal energy supply. An in-depth sensitivity analysis was investigated considering a deep borehole closed-loop heat exchanger (DBHE) to overcome the current limitations of deep EGS. A T2Well/EOS1 model previously calibrated on an experimental DBHE in Hawaii was adapted to the current NWG 55-29 well at the Newberry volcano site in Central Oregon. A sensitivity analysis was carried out, including parameters such as the working fluid mass flow rate, the casing and cement thermal properties, and the wellbore radii dimensions. The results conclude the highest energy flow rate to be 1.5 MW, after an annulus radii increase and an imposed mass flow rate of 5 kg/s. At 3 kg/s, the DBHE yielded an energy flow rate a factor of 3.5 lower than the NWG 55-29 conventional design. Despite this loss, the sensitivity analysis allows an assessment of the key thermodynamics within the wellbore and provides a valuable insight into how heat is lost/gained throughout the system. This analysis was performed under the assumption of subcritical conditions, and could aid the development of unconventional designs within future EGS work like the Newberry Deep Drilling Project (NDDP). Requirements for further software development are briefly discussed, which would facilitate the modelling of unconventional geothermal wells in supercritical systems to support EGS projects that could extend to deeper depths.

scholarly journals Cooling Performance Enhancement of Air-Cooled Condensers by Guiding Air Flow

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3503
Author(s):  
Huang ◽  
Chen ◽  
Yang ◽  
Du ◽  
Yang
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Dissipation ◽  
Performance Enhancement ◽  
Cooling System ◽  
Wind Effects ◽  
Cooling Performance ◽  
Air Cooled Condensers ◽  
Arc Shape

Adverse wind effects on the thermo-flow performances of air-cooled condensers (ACCs) can be effectively restrained by wind-proof devices, such as air deflectors. Based on a 2 × 300 MW coal-fired power generation unit, two types (plane and arc) of air deflectors were installed beneath the peripheral fans to improve the ACC’s cooling performance. With and without air deflectors, the air velocity, temperature, and pressure fields near the ACCs were simulated and analyzed in various windy conditions. The total air mass flow rate and unit back pressure were calculated and compared. The results show that, with the guidance of deflectors, reverse flows are obviously suppressed in the upwind condenser cells under windy conditions, which is conducive to an increased mass flow rate and heat dissipation and, subsequently, introduces a favorable thermo-flow performance of the cooling system. When the wind speed increases, the leading flow effect of the air deflectors improves, and improvements in the ACC’s performance in the wind directions of 45° and –45° are more satisfactory. However, hot plume recirculation may impede performance when the wind direction is 0°. For all cases, air deflectors in an arc shape are recommended to restrain the disadvantageous wind effects.

scholarly journals Analytical and Experimental Investigation of a Plate Fin Heat Exchanger at Cryogenics Temperature

2021 ◽  
Vol 39 (4) ◽  
pp. 1225-1235
Author(s):  
Ajay K. Gupta ◽  
Manoj Kumar ◽  
Ranjit K. Sahoo ◽  
Sunil K. Sarangi
Keyword(s):  
Heat Exchanger ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Cryogenic Temperature ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Compact Size

Plate-fin heat exchangers provide a broad range of applications in many cryogenic industries for liquefaction and separation of gasses because of their excellent technical advantages such as high effectiveness, compact size, etc. Correlations are available for the design of a plate-fin heat exchanger, but experimental investigations are few at cryogenic temperature. In the present study, a cryogenic heat exchanger test setup has been designed and fabricated to investigate the performance of plate-fin heat exchanger at cryogenic temperature. Major parameters (Colburn factor, Friction factor, etc.) that affect the performance of plate-fin heat exchangers are provided concisely. The effect of mass flow rate and inlet temperature on the effectiveness and pressure drop of the heat exchanger are investigated. It is observed that with an increase in mass flow rate effectiveness and pressure drop increases. The present setup emphasis the systematic procedure to perform the experiment based on cryogenic operating conditions and represent its uncertainties level.

scholarly journals Thermal Characteristics Analysis on Multi- Heat Pipe Induced Heat Exchanger

2019 ◽  
Vol 9 (2S2) ◽  
pp. 143-147 ◽  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Pipe ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Cold Water ◽  
Hot Water ◽  
Working Fluid ◽  
Physical Parameters

In this investigation of multi heat pipe induced in heat exchanger shows the developments in heat transfer is to improve the efficiency of heat exchangers. Water is used as a heat transfer fluid and acetone is used as a working fluid. Rotameter is set to measure the flow rate of cold water and hot water. To maintain the parameter as experimental setup. Then set the mass flow rate of hot water as 40 LPH, 60LPH, 80 LPH, 100LPH, 120 LPH and mass flow rate of cold water as 20 LPH, 30 LPH, 40 LPH, 50 LPH, and 60 LPH. Then 40 C, 45 ºC, 50 ºC, 55 C, 60 ºC are the temperatures of hot water at inlet are maintained. To find some various physical parameters of Qc , hc , Re ,, Pr , Rth. The maximum effectiveness of the investigation obtained from condition of Thi 60 C, Tci 32 C and 100 LPH mhi, 60 LPH mci the maximum effectiveness attained as 57.25. Then the mhi as 100 LPH, mci as 60 LPH and Thi at 40 C as 37.6%. It shows the effectiveness get increased about 34.3 to the maximum conditions.

Effect of Mass Flow Rate of Inlet Gas on Holdup Mass of Solidcyclone Heat Exchanger

2014 ◽  
Vol 592-594 ◽  
pp. 1498-1502 ◽  
Author(s):  
T. Mothilal ◽  
K. Pitchandi
Keyword(s):  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
High Efficiency ◽  
Solid Particles ◽  
Operating Parameters ◽  
Water Removal ◽  
Solvent Recovery ◽  
Solid Feed Rate

Effect of mass flow rate of inlet gas on holdup mass in a high efficiency cyclone has been performed. Cyclone as heat transfer equipment may be used for drying, solidification, water removal, solvent recovery, sublimation, chemical reaction and oxidation. In all such cases, performance of cyclone depends on the surface area of the solid particles inside the cyclone. The holdup varies with the variation in operating parameters. This proposed work will present an effect of mass flow rate of inlet gas on cyclone heat exchanger and calculation of holdup mass by varying the mass flow rate of inlet gas, solid feed rate and diameter of the particle.

Flashing Flow Mechanisms of HFC-134a and HFC-410a Through Short-Tube Orifices

2011 ◽  
Author(s):  
Kitti Nilpueng ◽  
Somchai Wongwises
Keyword(s):  
Temperature Distribution ◽  
Pressure Distribution ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Operating Conditions ◽  
Evaporator Temperature ◽  
Hfc 134A ◽  
Flow Mechanisms ◽  
Short Tube

In this study, the flow mechanisms of HFC-134a and HFC-410A, including flow pattern, pressure distribution, temperature distribution, and mass flow rate inside short-tube orifice are presented and compared under the same working temperature. The test runs are performed at condenser temperature ranging between 35 and 45°C, evaporator temperature ranging between 2 and 12°C, and degree of subcooling ranging between 1 and 12 °C. The results show that the temperature distribution along the short-tube orifice obtained from HFC-410A is slightly higher than that obtained from HFC-134a. On the other hand, the pressure distribution between both refrigerants shows the large difference. It is also found that the tendency of mass flow rate obtained from HFC-134a almost coincides with those obtained HFC-410A as the operating conditions and short-tube orifice size are varied. However, the average mass flow rate of HFC-134a is slightly lower than that of HFC-410A.

Transient Response of a Cross Flow Heat Exchanger Subjected to Temperature and Flow Perturbations

2015 ◽  
Author(s):  
Karthik Silaipillayarputhur ◽  
Stephen A. Idem
Keyword(s):  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Transient Performance ◽  
Numerical Predictions ◽  
Minimum Capacity ◽  
Flow Heat

The transient performance of a multi-pass cross flow heat exchanger subjected to temperature and mass flow rate perturbations, where the heat exchanger flow circuiting is neither parallel flow nor counter flow, is considered in this work. A detailed numerical study was performed for representative single-pass, two-pass, and three-pass heat exchangers. Numerical predictions were obtained for cases where the minimum capacity rate fluid was subjected to a step change in inlet temperature in absence of mass flow rate perturbations. Likewise, numerical predictions were obtained for the heat exchangers operating initially at steady state, where a step mass flow rate change of the minimum capacity rate fluid was imposed in the absence of any fluid temperature perturbations. The transient performance of this particular heat exchanger configuration subjected to these temperature and flow disturbances has not been discussed previously in the available literature. In the present study the energy balance equations for the hot and cold fluids and the heat exchanger wall were solved using an implicit central finite difference method. A parametric study was conducted by varying the dimensionless quantities that govern the transient response of the heat exchanger over a typical range of values. Because of the storage of energy in the heat exchanger wall, and finite propagation times associated with the inlet perturbations, the outlet temperatures of both fluids do not respond instantaneously. The results are compared with previously published transient performance predictions of multi-pass counter flow and parallel flow heat exchangers.

scholarly journals Experimental Investigation Of Heat Transfer Characteristics Of Nanofluid Using Parallel Flow, Counter Flow And Shell And Tube Heat Exchanger

2015 ◽  
Vol 62 (4) ◽  
pp. 509-522 ◽  
Author(s):  
R. Dharmalingam ◽  
K.K. Sivagnanaprabhu ◽  
J. Yogaraja ◽  
S. Gunasekaran ◽  
R. Mohan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Tube Heat Exchanger ◽  
Overall Heat Transfer Coefficient ◽  
Shell And Tube

Abstract Cooling is indispensable for maintaining the desired performance and reliability over a very huge variety of products like electronic devices, computer, automobiles, high power laser system etc. Apart from the heat load amplification and heat fluxes caused by many industrial products, cooling is one of the major technical challenges encountered by the industries like manufacturing sectors, transportation, microelectronics, etc. Normally water, ethylene glycol and oil are being used as the fluid to carry away the heat in these devices. The development of nanofluid generally shows a better heat transfer characteristics than the water. This research work summarizes the experimental study of the forced convective heat transfer and flow characteristics of a nanofluid consisting of water and 1% Al2O3 (volume concentration) nanoparticle flowing in a parallel flow, counter flow and shell and tube heat exchanger under laminar flow conditions. The Al2O3 nanoparticles of about 50 nm diameter are used in this work. Three different mass flow rates have been selected and the experiments have been conducted and their results are reported. This result portrays that the overall heat transfer coefficient and dimensionless Nusselt number of nanofluid is slightly higher than that of the base liquid at same mass flow rate at same inlet temperature. From the experimental result it is clear that the overall heat transfer coefficient of the nanofluid increases with an increase in the mass flow rate. It shows that whenever mass flow rate increases, the overall heat transfer coefficient along with Nusselt number eventually increases irrespective of flow direction. It was also found that during the increase in mass flow rate LMTD value ultimately decreases irrespective of flow direction. However, shell and tube heat exchanger provides better heat transfer characteristics than parallel and counter flow heat exchanger due to multi pass flow of nanofluid. The overall heat transfer coefficient, Nusselt number and logarithmic mean temperature difference of the water and Al2O3 /water nanofluid are also studied and the results are plotted graphically.

scholarly journals Harvesting Cooling Effect on LPG-Fueled Vehicles for Mini Cooler: A Lab-Scale Investigation

2019 ◽  
Vol 4 (1) ◽  
pp. 39
Author(s):  
Muji Setiyo ◽  
Noto Widodo ◽  
Bagiyo Condro Purnomo ◽  
Suroto Munahar ◽  
Muhammad Andi Rahmawan ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Engine Speed ◽  
Water Mass ◽  
Cooling Effect ◽  
Cooling Power ◽  
Heat Absorption ◽  
Water Mass Flow Rate

This article presents an investigation of the actual cooling effect on a lab-scale prototype of LPG-fueled vehicles. The cooling effect is obtained from heat absorption by LPG on the vaporizer. Water with a mass flow rate of 1, 2 and 3 lpm is flowed from the cooling box to the LPG evaporator and flow back to the cooling box. The car used in this study has a capacity of 1500 cc that rotates 1000, 1500, and 2000 rpm. The results showed that there was a relationship between cooling power with the increase in engine speed and mass flow rate of water that crosses the evaporator. The biggest cooling power is 378 Watts at 1000 rpm with a water mass flow rate of 3 lpm.

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