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.

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.

Forced Flow and Convective Heat Transfer of Phase Change Material Slurry in the Heat Exchangers

2010 ◽  
Author(s):  
Peng Zhang ◽  
Zhiwei Ma ◽  
Ruzhu Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Phase Change ◽  
Phase Change Material ◽  
Flow Rate ◽  
Tetrabutylammonium Bromide ◽  
Forced Flow ◽  
Experimental Investigations ◽  
Cooling Power ◽  
Change Material

The application of phase change material slurry to the refrigeration and air conditioning system opens a new way for energy saving and reduction of the quantity of refrigerant in the system, because it can serve as both the energy storage and transportation media in the secondary loop which is responsible for distributing the cooling power. In the present study, the experimental investigations of the forced flow and heat transfer characteristics of Tetrabutylammonium Bromide (TBAB in abbreviation) clathrate hydrate slurry (CHS) in both the plate heat exchanger (PHE) and double-tube heat exchanger (DHE) are carried out. It is found out that the pressure drop in the PHE is about 5–50 kPa at the flow rate of 2–14 L/min and is about 2–30 kPa at the flow rate of 3–14 L/min, which is nearly 2 times of that of the chilled water. The overall heat transfer coefficient is in the range of 2500–5000 W/(m2K) for TBAB CHS in the PHE and is about 1500–3500 W/(m2K) in the DHE, which are both higher than that of TBAB aqueous solution flow because of the involvement of the phase change of TBAB CHS.

Determining Gas Flow Rate and Formation Thermal Conductivity from Pressure and Temperature Profiles in Vertical Well

2012 ◽  
Author(s):  
Emile Eli Barrett ◽  
Imran Abbasy ◽  
Chii Rong Wu ◽  
Zhenjiang You ◽  
Pavel G. Bedrikovetsky
Keyword(s):  
Thermal Conductivity ◽  
Flow Rate ◽  
Gas Flow ◽  
Temperature Profiles ◽  
Gas Flow Rate ◽  
Vertical Well

Effect of Additional MnFe2O4 on a Combination of EG-Water Nanofluid and Volumetric Flowrate Variations towards Heat Transfer in Shell and Tube Heat Exchanger System

2020 ◽  
Vol 851 ◽  
pp. 38-46
Author(s):  
Avita Ayu Permanasari ◽  
Fadel Fadillah ◽  
Poppy Puspitasari ◽  
Sukarni Sukarni
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Flow Rate ◽  
Base Fluid ◽  
Volume Fraction ◽  
Volumetric Flow Rate ◽  
Shell And Tube ◽  
Water Base ◽  
Volumetric Flowrate

Nanofluid is an efficient fluid when used in heat exchanger system because of its larger thermal conductivity compared to conventional fluids such as water, oil, and ethylene glycol (EG). This research used MnFe2O4 nanoparticle due to its higher magnetic sensitivity compared to other ferrite nanoparticles and larger thermal conductivity than TiO2. This research used the MnFe2O4 nanoparticle with a combination of EG-Water base fluids in ratios of 40:60, 60:40, and 80:20. MnFe2O4 nanofluid mixed with EG-Water base fluids was made using the two-step method with 0.05% MnFe2O4 volume fraction in each base fluid ratio. This research used shell and tube type heat exchanger with heat temperature of 60°C and cold temperature of 26°C that were carried out at volumetric flowrate in each base fluid ratio for 0.22 l/m, 0.44 l/m, and 0.66 l/m. This research aimed to find the best combination ratio of EG-Water in thermophysical (thermal conductivity, specific heat, density, and viscosity) and to find the effect of volumetric flowrate variations on the heat exchange characteristics (the Reynold number, the Nusselt number, ∆T LMTD, convection coefficient, heat transfer, and overall heat transfer coefficient). The results of this research were that the sample of EG-Water with 40:60 ratio had the best heat transfer characteristics compared to samples with 60:40 and 80:20 ratios. Meanwhile, for the volumetric flow rate, a higher volumetric flow rate resulted in a larger result.

scholarly journals Performance Study of Direct Integration of Phase Change Material into an Innovative Evaporator of a Simple Vapour Compression System

2020 ◽  
Vol 10 (13) ◽  
pp. 4649 ◽  
Author(s):  
Boniface Dominick Mselle ◽  
David Vérez ◽  
Gabriel Zsembinszki ◽  
Emiliano Borri ◽  
Luisa F. Cabeza
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Phase Change ◽  
Flow Rate ◽  
Cooling Capacity ◽  
Heat Transfer Fluid ◽  
Cooling Power ◽  
Direct Integration ◽  
Compression System ◽  
Vapour Compression

This paper experimentally investigates the direct integration of 3.15 kg of phase change materials (PCM) into a standard vapour compression system of variable cooling capacity, through an innovative lab-scale refrigerant-PCM-water heat exchanger (RPW-HEX), replacing the conventional evaporator. Its performance was studied in three operating modes: charging, discharging, and direct heat transfer between the three fluids. In the charging mode, a maximum energy of 300 kJ can be stored in the PCM for the cooling capacity at 30% of the maximum value. By doubling the cooling power, the duration of charging is reduced by 50%, while the energy stored is only reduced by 13%. In the discharging mode, the process duration is reduced from 25 min to 9 min by increasing the heat transfer fluid (HTF) flow rate from 50 L·h−1 to 150 L·h−1. In the direct heat transfer mode, the energy stored in the PCM depends on both the cooling power and the HTF flow rate, and can vary from 220 kJ for a cooling power at 30% and HTF flow rate of 50 L·h−1 to 4 kJ for a compressor power at 15% and a HTF flow rate of 150 L·h−1. The novel heat exchanger is a feasible solution to implement latent energy storage in vapour compression systems resulting to a compact and less complex system.

Experimental Investigation of the Hydraulic and Thermal Performance of a Phase Change Material Slurry in the Heat Exchangers

2011 ◽  
Vol 3 (1) ◽  
Author(s):  
P. Zhang ◽  
Z. W. Ma ◽  
R. Z. Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Phase Change ◽  
Phase Change Material ◽  
Flow Rate ◽  
Tetrabutylammonium Bromide ◽  
Forced Flow ◽  
Experimental Investigations ◽  
Cooling Power ◽  
Change Material

The application of phase change material slurry to the refrigeration and air conditioning system opens a new way for energy saving and reduction of the quantity of refrigerant in the system involved because it can serve as both the energy storage and the transportation media in the secondary loop, which is responsible for distributing the cooling power. In the present study, the experimental investigations of the forced flow and heat transfer characteristics of tetrabutylammonium bromide (TBAB) clathrate hydrate slurry (CHS) in both the plate heat exchanger (PHE) and the double-tube heat exchanger (DHE) are carried out. It is found out that the pressure drop in the PHE is about 3.0–50.0 kPa at the flow rate of 2.5–13.0 L/min (0.15–0.78 m3∕h)and is about 1.0–27.0 kPa at the flow rate of 3.0–14.0 L/min (0.18–0.84 m3∕h) in the DHE, which is nearly 2 times of that of the chilled water. The overall heat transfer coefficient is in the range of 2500–5000 W/(m2 K) for TBAB CHS in the PHE and is about 1500–3500 W/(m2 K) in the DHE, which are both higher than that of TBAB aqueous solution flow because of the involvement of the phase change of TBAB CHS.

The error in determining the flow rate of the injected water as measured by a downhole thermal conductivity flowmeter

2017 ◽  
pp. 135-137
Author(s):  
V.F. Nazarov ◽  
◽  
V.K. Mukhutdinov ◽  
R.F. Ismagilov ◽  
A.Yu. Balykin ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Flow Rate

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.

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