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.

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).

scholarly journals Validation of the generalized model of two-phase thermosyphon loop based on experimental measurements of volumetric flow rate

2016 ◽  
Vol 37 (3) ◽  
pp. 109-138 ◽  
Author(s):  
Henryk Bieliński
Keyword(s):  
Steady State ◽  
Flow Rate ◽  
Vertical Section ◽  
Volumetric Flow Rate ◽  
Working Fluid ◽  
Two Phase ◽  
Generalized Model ◽  
Flow Models ◽  
Theoretical Predictions ◽  
The One

AbstractThe current paper presents the experimental validation of the generalized model of the two-phase thermosyphon loop. The generalized model is based on mass, momentum, and energy balances in the evaporators, rising tube, condensers and the falling tube. The theoretical analysis and the experimental data have been obtained for a new designed variant. The variant refers to a thermosyphon loop with both minichannels and conventional tubes. The thermosyphon loop consists of an evaporator on the lower vertical section and a condenser on the upper vertical section. The one-dimensional homogeneous and separated two-phase flow models were used in calculations. The latest minichannel heat transfer correlations available in literature were applied. A numerical analysis of the volumetric flow rate in the steady-state has been done. The experiment was conducted on a specially designed test apparatus. Ultrapure water was used as a working fluid. The results show that the theoretical predictions are in good agreement with the measured volumetric flow rate at steady-state.

Performance and Development of a Miniature Rotary Shaft Pump

2005 ◽  
Vol 127 (4) ◽  
pp. 752-760 ◽  
Author(s):  
Danny Blanchard ◽  
Phil Ligrani ◽  
Bruce Gale
Keyword(s):  
Flow Rate ◽  
Pressure Rise ◽  
Electronics Cooling ◽  
Maximum Flow ◽  
Operating Conditions ◽  
Working Fluid ◽  
Hydraulic Efficiency ◽  
Potential Applications ◽  
Total Analysis ◽  
And Performance

The development and performance of a novel miniature pump called the rotary shaft pump (RSP) is described. The impeller is made by boring a 1.168 mm hole in one end of a 2.38 mm dia shaft and cutting slots in the side of the shaft at the bottom of the bored hole such that the metal between the slots defines the impeller blades. The impeller blades and slots are 0.38 mm tall. Several impeller designs are tested over a range of operating conditions. Pump performance characteristics, including pressure rise, hydraulic efficiency, slip factor, and flow rate, are presented for several different pump configurations, with maximum flow rate and pressure rise of 64.9ml∕min and 2.1 kPa, respectively, when the working fluid is water. Potential applications include transport of biomedical fluids, drug delivery, total analysis systems, and electronics cooling.

Energy and Exergy Analysis of Marquise Shaped Channel Flat Plate Solar Collector Using Al2O3–Water Nanofluid and Water

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Sahil Arora ◽  
Geleta Fekadu ◽  
Sudhakar Subudhi
Keyword(s):  
Flat Plate ◽  
Flow Rate ◽  
Volume Fraction ◽  
Pure Water ◽  
Maximum Energy ◽  
Working Fluid ◽  
Absorber Plate ◽  
Energy And Exergy ◽  
Aluminum Plates ◽  
Flat Plate Collector

The present study deals with the experimental performance of a Marquise shaped channel solar flat-plate collector using Al2O3/water nanofluid and base fluid (pure water). The experimental setup comprises a special type of solar flat plate collector, closed working fluid systems, and the measurement devices. The absorber plate is made of two aluminum plates sandwiched together with Marquise-shaped flow channels. The volume fraction of 0.1% of Al2O3/water nanofluid is used for this study. The various parameters used to investigate performance of the collector energy and exergy efficiency are collector inlet and outlet fluid temperatures, mass flow rate of the fluid, solar radiation, and ambient temperature. The flow rate of nanofluid and water varies from 1 to 5 lpm. The maximum energy efficiencies attained are 83.17% and 59.72%, whereas the maximum exergy efficiencies obtained are 18.73% and 12.29% for the 20 nm—Al2O3/water nanofluids and pure water, respectively, at the flow rate of 3 lpm. These higher efficiencies may be due to the use of nanofluids and the sophisticated design of the absorber plate with the Marquise shaped channel.

scholarly journals Efficiency Improvement of a Photovoltaic Thermal (PVT) System Using Nanofluids

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3063 ◽  
Author(s):  
Joo Hee Lee ◽  
Seong Geon Hwang ◽  
Gwi Hyun Lee
Keyword(s):  
Flat Plate ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Measurement Errors ◽  
Efficiency Analysis ◽  
Working Fluid ◽  
Efficiency Improvement ◽  
Flow Rates ◽  
Electrical Efficiency ◽  
Water Based

Many studies and considerable international efforts have gone into reducing greenhouse gas emissions. This study was carried out to improve the efficiency of flat-plate photovoltaic thermal (PVT) systems, which use solar energy to produce heat and electricity simultaneously. An efficiency analysis was performed with various flow rates of water as the working fluid. The flow rate, which affects the performance of the PVT system, showed the highest efficiency at 3 L/min compared with 1, 2, and 4 L/min. Additionally, the effects of nanofluids (CuO/water, Al2O3/water) and water as working fluids on the efficiency of the PVT system were investigated. The results showed that the thermal and electrical efficiencies of the PVT system using CuO/water as a nanofluid were increased by 21.30% and 0.07% compared to the water-based system, respectively. However, the increase in electrical efficiency was not significant because this increase may be due to measurement errors. The PVT system using Al2O3/water as a nanofluid improved the thermal efficiency by 15.14%, but there was no difference in the electrical efficiency between water and Al2O3/water-based systems.

scholarly journals Numerical study of flat plate solar collector performance with square shape wicked evaporator

2019 ◽  
Vol 12 (2) ◽  
pp. 90-97
Author(s):  
Basil Noori Merzah ◽  
Majid H. Majeed ◽  
Fouad A. Saleh
Keyword(s):  
Flat Plate ◽  
Heat Pipe ◽  
Flow Rate ◽  
Solar Collector ◽  
Numerical Study ◽  
Charge Ratio ◽  
Working Fluid ◽  
Evaporator Section ◽  
Fill Charge Ratio ◽  
Flat Plate Solar Collector

In this work, a system of a heat pipe is implemented to improve the performance of flat plate solar collector. The model is represented by square shape portion of the evaporator section of wicked heat pipe with a constant total length of 510 mm, and the evaporator section inclined by an angle of 30o. In this models the evaporator, adiabatic and condenser lengths are 140mm, 140mm, and 230mm respectively. The omitted energies from sunlight simulator are 200, 400, 600, 800 and 1000 W/m2 which is close to the normal solar energy in Iraq. The working fluid for all models is water with fill charge ratio of 240%. The efficiency of the solar collector is investigated with three values of condenser inlet water temperatures, namely (12, 16 and 20o C). The numerical result showed an optimum volume flow rate of cooling water in condenser at which the efficiency of collector is a maximum. This optimum agree well with the ASHRAE standard volume of flow rate for conventional tasting for flat plate solar collector. When the radiation incident increases the thermal resistance of wicked heat pipe is decreases, where the heat transfer from the evaporator to condenser increases. The numerical results showed the performance of solar collector with square shape evaporator greater than other types of evaporator as a ratio 15 %.

Transient Simulation of Absorption Machines

1982 ◽  
Vol 104 (3) ◽  
pp. 197-203 ◽  
Author(s):  
D. K. Anand ◽  
R. W. Allen ◽  
B. Kumar
Keyword(s):  
Steady State ◽  
Lithium Bromide ◽  
Working Fluid ◽  
Cooling Load ◽  
Space Cooling ◽  
Start Up ◽  
Residual Capacity ◽  
Insight Into ◽  
Significant Factors ◽  
Steady State Performance

This paper presents a model for a water-cooled Lithium-Bromide/water absorption chiller and predicts its transient response both during the start-up phase and during the shutoff period. The simulation model incorporates such influencing factors as the thermodynamic properties of the working fluid, the absorbent, the heat-transfer configuration of different components of the chiller and related physical data. The time constants of different components are controlled by a set of key parameters that have been identified in this study. The results show a variable but at times significant amount of time delay before the chiller capacity gets close to its steady-state value. The model is intended to provide an insight into the mechanism of build-up to steady-state performance. By recognizing the significant factors contributing to transient degradation, steps can be taken to reduce such degradation. The evaluation of the residual capacity in the shut-off period will yield more realistic estimates of chiller COP for a chiller satisfying dynamic space cooling load.

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