Investigation of a Capillary Assisted Thermosyphon (CAT) for Shipboard Electronics Cooling

Volume 4 ◽  
2004 ◽  
Author(s):  
E. H. Larsen ◽  
M. Cerza ◽  
A. N. Smith ◽  
C. Thomas Conroy
Keyword(s):  
Flat Plate ◽  
Heat Input ◽  
Power Dissipation ◽  
Water Flow Rate ◽  
Cooling Water ◽  
Electronics Cooling ◽  
Working Fluid ◽  
Cold Plate ◽  
Capillary Pumped Loop ◽  
Forced Circulation

As microprocessors shrink in size and increase in power dissipation levels, the current need for advanced electronics cooling techniques is paramount since power dissipation levels are rapidly exceeding the capabilities of forced air convection cooling. This paper reports an investigation of using a capillary assisted thermosyphon for the shipboard cooling of electronics components. The capillary assisted thermosyphon differs from the capillary pumped loop or loop heat pipe system in that the basic cooling loop is based on a thermosyphon. The capillary assist comes from the fact that there is a wicking structure in the flat evaporator plate, however, the wicking structure is there to spread the working fluid across the flat plate evaporator in the areas under the heat sources. This differs from a capillary pumped loop in that the wick structure does not produce a capillary pumping head from the liquid return to the vapor outlet side of the evaporator. In fact, the liquid return and vapor outlet are almost at the same pressure. The forced circulation in the thermosyphon is caused by a gravity head between the condenser cold plate and the flat plate evaporator. An experimental facility for conducting research on capillary assisted thermosyphon was developed. In order to simulate the shipboard cooling water encountered at various locations of the ocean, the heat sink temperature of the facility could be varied. A vertical flat plate, CAT evaporator was designed and tested under thermal sink temperatures of 4, 21 and 37°C. The condenser cold plate cooling water flow rate varied from 0.38 to 3 GPM. The heat input varied from 250 to 1500 W evenly spread over the area of the evaporator. The CAT flat plate evaporator performed very well under this range of heat inputs, sink temperatures, and cold plate flow rates. The main result obtained showed that as heat input increased the amount of subcooling between the evaporator vapor outlet line and liquid return line increased. This subcooling did not hinder thermal performance as measured by the internal operating temperature.

The Effect of Ship Tilt and Pitch on a Capillary Assisted Thermosyphon (CAT) for Shipboard Electronics Cooling

2003 ◽  
Author(s):  
E. H. Larsen ◽  
A. N. Smith ◽  
M. Cerza ◽  
C. Thomas Conroy
Keyword(s):  
Flat Plate ◽  
Heat Input ◽  
Power Dissipation ◽  
Cooling Water ◽  
Electronics Cooling ◽  
Working Fluid ◽  
Cold Plate ◽  
Capillary Pumped Loop ◽  
Flat Evaporator ◽  
Vertical Flat Plate

As microprocessors shrink in size and increase in power dissipation levels, the current need for advanced electronics cooling techniques is paramount. Power dissipation levels are rapidly exceeding the capabilities of forced air convection cooling. This paper reports an investigation of using a capillary assisted thermosyphon (CAT) for the shipboard cooling of electronics components. The CAT differs from the capillary pumped loop (CPL) or loop heat pipe (LHP) system in that the basic cooling loop is based on a thermosyphon. The capillary assist comes from the fact that there is a wicking structure in the flat evaporator plate. The wicking structure is there to spread the working fluid across the vertical flat plate evaporator to the areas under the heat sources. This differs from a capillary pumped loop in that the capillary pumping action of the wick structure does not produce the sole pumping head from the liquid return to the vapor outlet side of the evaporator. In fact, the liquid return and vapor outlet are almost at the same pressure. The forced circulation in the thermosyphon is caused by a gravity head between the condenser cold plate and the flat plate evaporator. An experimental facility for conducting research on a CAT was developed. In order to simulate the shipboard cooling water encountered at various locations of the ocean, the heat sink temperature of the facility was varied. A vertical flat plate, CAT evaporator was designed and tested with a thermal sink temperature of 21° C. The condenser cold plate cooling water flowrate was set at 3.8 lpm. The heat input was held constant at 1500 W for the independent tilt and pitch cases. For the extreme tilt and pitch combined case, the heat input varied from 400 to 2000 W. The flat evaporator plate was tilted from side to side over a range +/− 45 degrees from vertical and the plate was pitched fore and aft over a range of +/− 45 degrees. This tilt and pitch orientation was to simulate that orientation which a ship might undergo in various sea states. In addition an extreme case which consisted of a 45 degree tilt and a 45 degree pitch was tested and compared to the normal vertical geometry. Results indicate that the CAT loop was very robust and handled all geometric orientations with minimal degradation in operating temperature performance.

The Effect of Initial Charge on the Steady-State Operating Performance of a Capillary Assisted Thermosyphon

2005 ◽  
Author(s):  
V. Tudor ◽  
M. Cerza ◽  
A. N. Smith ◽  
C. T. Conroy
Keyword(s):  
Flat Plate ◽  
Electric Propulsion ◽  
Operating Temperature ◽  
Working Fluid ◽  
Cold Plate ◽  
Capillary Pumped Loop ◽  
Forced Circulation ◽  
Fill Ratio ◽  
Initial Charge ◽  
Wick Structure

The future capabilities of naval ships will be directly related to the electronic components used in advanced radar systems, fire control systems, electric propulsion and electric weapons. Modern electronics continue to grow in speed and functionality but shrink in size and mass, causing the power density to dramatically increase. Thermal management is becoming a major issue for the modern electronic Navy. An experimental investigation on the effect of liquid charge in a capillary assisted thermosyphon (CAT) loop for the shipboard cooling of electronics components has been conducted. The employed CAT loop differs from the capillary pumped loop or loop heat pipe system, in that the basic cooling loop is based on a thermosyphon. A wick structure located on the walls of the evaporator plate provides the capillary assistance needed to spread the working fluid (i.e. water) across the flat plate evaporator in the areas under the heat sources. This differs from a capillary pumped loop in that the wick structure does not produce a significant capillary pumping head from the liquid return to the vapor outlet side of the evaporator. The forced circulation in the CAT loop is caused by a gravity head between the condenser cold plate and the flat plate evaporator. The influence of the liquid charge on the CAT loop performance was studied for a fixed sink temperature and a range of heat inputs from 250W to 1000W. The initial liquid charge was varied from 50 ml to 200 ml (i.e. 16% to 24% evaporator fill ratio). The evaporator fill ratio was defined in this study as the ratio of the initial charge to the total volume of the evaporator. The condenser cold plate cooling water flow rate was set to 63.088 ml/sec. The CAT flat plate evaporator performed very well under this range of heat inputs, sink temperature, and initial charges. The experimental results obtained indicated that as heat input and the liquid charge increased or decreased above/below an optimum value, the operating temperature in the evaporator increased. The CAT loop flow dynamics also changed as a function of the initial liquid charge. Overall these effects did not hinder the thermal performance as measured by the internal operating temperature of the evaporator. An optimal charge was observed at an evaporator fill ratio of 40% (i.e. 125ml).

Start Up and Transient Response to Power Input of a Capillary Assisted Thermosyphon for Shipboard Electronics Cooling

2010 ◽  
Author(s):  
V. Tudor ◽  
M. Cerza
Keyword(s):  
Steady State ◽  
Flat Plate ◽  
Transient Response ◽  
Flow Rate ◽  
Heat Input ◽  
Electric Propulsion ◽  
Electronics Cooling ◽  
Working Fluid ◽  
Cold Plate ◽  
Start Up

The future capabilities of naval ships will be directly related to the electronic components used in advanced radar systems, fire control systems, electric propulsion and even electric weapons. The next generation of naval warships will fall under the concept of an all electric ship, where turbines convert all the power produced by the engine into electricity. This electrical power can then be distributed given the ship’s mission and operating profile. The current need for advanced electronics cooling techniques is paramount since power dissipation levels are rapidly exceeding the capabilities of forced air convection cooling. This paper reports an experimental investigation of the start-up and transient response to heat load change of a capillary assisted thermosyphon (CAT) for the shipboard cooling of electronics components. The capillary assisted thermosyphon differs from a capillary pumped loop or loop heat pipe system in that the basic cooling-loop is based on a thermosyphon. The capillary assist comes from the fact that there is a wicking structure in the flat evaporator plate. The wicking structure allows uniformly spread of the working fluid across the flat plate evaporator in the areas under the heat sources as well as providing additional capillary pumping assist to the loop. A vertical flat plate, CAT evaporator was designed and tested under a fixed thermal sink temperature of 21°C. The condenser cold plate cooling water flow rate was fixed as 3.785 liters per minute (i.e. 1 gpm). The heat input varied from 250 to 1000W — evenly spread over the area of the evaporator. The CAT flat plate evaporator performed very well under this range of heat inputs, sink temperature, and cold plate flow rate. The main result obtained showed that the CAT loop reached steady state operation within 10 min. to 15 min. The average plate temperature did not exceed 70°C for the maximum heat input of 1000W. The CAT evaporator operating temperature increased with increasing heat input for all conditions tested and reached 60°C at 1000W. The continuous and stable operation of the CAT loop during start-up, steady-state and during transient/sudden heat input variations indicates that the CAT loop is a viable solution for high flux electronics components cooling.

scholarly journals The Effect of Sink Temperature on a Capillary Pumped Loop Employing a Flat Evaporator and Shell and Tube Condenser

2001 ◽  
Author(s):  
M. Cerza ◽  
R. C. Herron ◽  
M. J. Harper
Keyword(s):  
Flat Plate ◽  
Heat Input ◽  
Heat Sink ◽  
Cooling Water ◽  
Large Degree ◽  
Heat Fluxes ◽  
Capillary Pumped Loop ◽  
Flat Evaporator ◽  
Conducting Research ◽  
Tube Condenser

Abstract An experimental facility for conducting research on capillary pumped loop (CPL) systems was developed. In order to simulate shipboard cooling water encountered at various locations of the ocean, the heat sink temperature of the facility could be varied. A flat plate, CPL evaporator was designed and tested under various heat sink temperatures. The sink temperature ranged from 274.3 to 305.2 K and the heat input varied from 250 to 800 W which corresponds to heat fluxes up to 1.8 W/cm2. The CPL flat plate evaporator performed very well under this range of heat input and sink temperatures. The main result obtained showed that a large degree of subcooling developed between the evaporator vapor outlet line and liquid return line. This condensate depression increased with increasing heat input.

Experimental Study of Solar Pond Coupled With Forced Circulation Crystallizer as Major Stages of Proposed Zero Discharge Desalination Process

2013 ◽  
Vol 6 (2) ◽  
Author(s):  
Farshad Farahbod ◽  
Sara Farahmand
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Water Flow Rate ◽  
Cooling Water ◽  
Treated Wastewater ◽  
Forced Circulation ◽  
Solar Pond ◽  
Cooling Water Flow Rate ◽  
Salt Crystals ◽  
Zero Discharge

Pretreatment, solar pond (SP), and forced circulation crystallizer (FCC) are the basic stages of one option to provide the goals of zero discharge desalination (ZDD) process. This work represents the performance of a solar pond that is coupled with forced circulation crystallizer as second and third stages of proposed zero discharge desalination process. The purpose of ZDD in this paper is gathering fresh water and saline crystals from effluent wastewater of the desalination unit of Mobin petrochemical complex. So, the SP unit is constructed after the pretreatment unit to concentrate the treated wastewater to about 20 wt. % as a suited feed for the FCC unit. Effects of solar insolation rate are investigated experimentally, during a year. In addition, the effect of cooling water flow rate of FCC on quality of effluent stream from SP as feed crystallizer is studied in this paper. The experimental results show the maximum evaporation rate from SP is obtained 5 l/(m2·d) when the insolation rate was about 2.5 × 104 kJ/(m2·d). Experiments show the suitable range of crystals growth (710 μm to 830 μm) in FCC is occurred when the cooling water flow rate in condenser is 9 kg/min. The size and the color of produced salt crystals will be optimized in this flow rate and energy consumption is measured as 6.98 kW·h.

scholarly journals Experimental Study of the Heat-Transfer Performance of an Extra-Long Gravity-Assisted Heat Pipe Aiming at Geothermal Heat Exploitation

2021 ◽  
Vol 13 (22) ◽  
pp. 12481
Author(s):  
Jiwen Cen ◽  
Feng Li ◽  
Tingliang Li ◽  
Wenbo Huang ◽  
Juanwen Chen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Water Flow Rate ◽  
Cooling Water ◽  
Filling Ratio ◽  
Working Fluid ◽  
Enhanced Geothermal Systems ◽  
Transfer Performance ◽  
Cooling Water Flow Rate

The installation and operation of enhanced geothermal systems (EGS) involves many challenges. These challenges include the high cost and high risk associated with the investment capital, potential large working-fluid leakage, corrosion of equipment, and subsiding land. A super-long heat pipe can be used for geothermal exploitation to avoid these problems. In this paper, a high aspect-ratio heat pipe (30 m long, 17 mm in inner diameter) is installed vertically. Experiments are then carried out to study its heat-transfer performance and characteristics using several filling ratios of deionized water, different heating powers, and various cooling-water flowrates. The results show that the optimal filling-ratio is about 40% of the volume of the vaporizing section of the heat pipe. Compared with a conventional short heat pipe, the extra-long heat pipe experiences significant thermal vibration. The oscillation frequency depends on the heating power and working-fluid filling ratio. With increasing cooling-water flow rate, the heat-transfer rate of the heat pipe increases before it reaches a plateau. In addition, we investigate the heat-transfer performance of the heat pipe for an extreme working-fluid filling ratio; the results indicate that the lower part of the heat pipe is filled with vapor, which reduces the heat-transfer to the top part. Based on the experimental data, guidelines for designing a heat pipe that can be really used for the exploitation of earth-deep geothermal energy are analyzed.

Integrated Flat Plate Heat Pipe-Pulsation Heat Pipe for the High-Flux Electronics Cooling

2014 ◽  
Vol 960-961 ◽  
pp. 389-393
Author(s):  
Ya Ping Zhang ◽  
J.G. Wang
Keyword(s):  
Flat Plate ◽  
Heat Pipe ◽  
Electronics Cooling ◽  
High Heat ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Electronic Components ◽  
Plate Heat ◽  
Effective Combination ◽  
Flat Plate Heat Pipe

A trend towards increasingly dense and compact architectures has led to unmanageably high heat fluxes in electronic components. A novel heat pipe will be developed. Heat pipe designed is based on the flat plate heat pipe and pulsation heat pipe effective combination. Channel quantity is greatly increased ,as well as compact and homogeneous red copper pulsation plank is severed as the wick，dense and connected channels are served as the passage of the working fluid.

Experimental Investigation of a Flat-Plate Closed-Loop Pulsating Heat Pipe

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Wessel W. Wits ◽  
Gerben Groeneveld ◽  
Henk Jan van Gerner
Keyword(s):  
Experimental Investigation ◽  
Flat Plate ◽  
Heat Pipe ◽  
Closed Loop ◽  
Electronics Cooling ◽  
Power Input ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Thermo Electric ◽  
Temperature And Pressure

The thermal performance and operating modi of a flat-plate closed-loop pulsating heat pipe (PHP) are experimentally observed. The PHP is manufactured through computer numerical controlled milling and vacuum brazing of stainless steel 316 L. Next to a plain closed-loop PHP, also one that promotes fluid circulation through passive Tesla-type valves was developed. Each channel has a 2 × 2 mm2 square cross section, and in total, 12 parallel channels fit within the 50 × 200 mm2 effective area. During the experimental investigation, the power input was increased from 20 W to 100 W, while cooling was performed using a thermo-electric cooler (TEC) and thermostat bath. Three working fluids were assessed: water, methanol, and ammonia. The PHP was charged with a 40% filling ratio. Thermal resistances were obtained for different inclination angles. It was observed that the PHP operates well in vertical evaporator-down orientation but not horizontally. Moreover, experiments show that the minimum operating orientation is between 15 and 30 deg. Two operating modi are observed, namely, the thermosyphon modus, without excessive fluctuations, and the pulsating modus, in which both the temperature and pressure responses oscillate frequently and violently. Overall thermal resistances were determined as low as 0.15 K/W (ammonia) up to 0.28 and 0.48 K/W (water and methanol, respectively) at a power input of 100 W in the vertical evaporator-down orientation. Infrared thermography was used to visualize the working fluid behavior within the PHPs. Infrared observations correlated well with temperature and pressure measurements. The experimental results demonstrated that the developed flat-plate PHP design, suitable for high-volume production, is a promising candidate for electronics cooling applications.

scholarly journals Experimental heat and mass transfer studies on horizontal falling film absorber using water-lithium bromide

2020 ◽  
Vol 24 (3 Part B) ◽  
pp. 1923-1934 ◽  
Author(s):  
Banu Arshi ◽  
N.M. Sudharsan
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Heat And Mass Transfer ◽  
Water Flow Rate ◽  
Lithium Bromide ◽  
Cooling Water ◽  
Horizontal Tube ◽  
Working Fluid ◽  
Falling Film ◽  
Cooling Water Flow Rate

Vapour absorption systems are more viable technology option in energy and environmental perspective in cooling and heating applications. Among the four major components of vapour absorption system, the absorber plays a vital role in deciding the performance, size and cost. Horizontal falling film absorbers comparatively contain good heat and mass transfer characteristics than other type of absorbers for working fluids such as water-lithium bromide. Literature shows that experimental approach of performance evaluation of absorber is more realistic and accurate than the theoretical approach. Hence in the present work, a detail experimental study has been done on horizontal tube falling film absorber using water-lithium bromide as a working fluid. The set-up consists of two major components viz. absorber and generator. Absorber contains three columns of tubes, with eight rows in each column. Detailed parametric study has been done by considering influence of spray density, cooling water-flow rate, cooling water temperature and concentration on solution temperatures, cooling water temperatures, inlet and outlet concentrations, heat flux, mass flux, heat transfer coefficient, and mass transfer coefficient with the help of plots. Results have been validated and literature gaps have been discussed.

Visualization and Evaporation Resistance Measurement for Groove-Wicked Flat Plate Heat Pipes

2011 ◽  
Author(s):  
Shwin-Chung Wong ◽  
Chung-Wei Chen
Keyword(s):  
Flat Plate ◽  
Heat Load ◽  
Cooling Water ◽  
Base Plate ◽  
Heat Pipes ◽  
Working Fluid ◽  
Plate Temperature ◽  
Plate Heat ◽  
Heated Zone ◽  
Liquid Front

This work experimentally studied the evaporation characteristics in groove-wicked flat-plate heat pipes. The parallel, U-shaped grooves have a width of 0.25 mm and a depth of 0.16 mm. Uniform heating was applied to the copper base plate near one end, and a cooling water jacket was connected at the other end. The evaporation resistance was calculated based on the difference of the plate temperature and the vapor temperature respectively under and above the center of the heated zone. Water was used as the working fluid. With stepwise increase of heat load, the behavior of the working fluid in the grooves was visualized, and the evaporation resistances were measured. Above a certain heat load, longitudinal liquid recession can be visualized with a steep-sloped liquid front. Behind the short liquid front is the accommodation region where the meniscus appeared to anchor on the top corners of the groove walls. Under a thermally stable situation, longitudinal oscillations of the liquid front existed in many grooves. Also, the liquid motion in different grooves seemed independent, forming a constantly varying zigzag front line. With increasing heat load, the liquid fronts gradually left the heated zone, accompanied by increasing plate temperatures. The evaporation resistance data appeared larger and more scattered than those associated with mesh or powder wicks in our published experiments, presumably due to the relatively large groove size and surface roughness from etching. No boiling was observed in all present tests. The evaporation resistances for groove wicks increase monotonically in response to the gradually enlarged dryout region with increasing heat load.

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