High Performance Micro-Grooved Evaporative Heat Transfer Surface for Low Grade Waste Heat Recovery Applications

2011 ◽  
Author(s):  
Vibhash Jha ◽  
Serguei Dessiatoun ◽  
Michael Ohadi ◽  
Amir Shooshtari ◽  
Ebrahim Al-Hajri
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Thermal Management ◽  
Flow Rate ◽  
High Performance ◽  
Waste Heat ◽  
Low Grade ◽  
Market Demand ◽  
Rate Range ◽  
Flow Rate Range

The continued demand for high performance electronic products and the simultaneous trend of miniaturization has raised the dissipated power and power densities to new unprecedented levels in electronic systems. Thermal management is becoming increasingly critical to the electronics industry to satisfy the increasing market demand for faster, smaller, lighter and more cost effective products. Utilization of waste heat for the purpose of cooling chip is a promising area for enhancing the thermal management and net energy efficiency of the system. This paper focuses on the development of a tubular microgrooved evaporator and its performance characterization based on heat transfer coefficients and pressure drop measurements. Channel with aspect ratio of 3:1 (channel width – 100 μm, channel height – 300 μm) microgrooved structure was used in the evaporator. The system has been tested with R134a as refrigerant for refrigerant flow rate range of 0.005–0.02 kg/s and water flow rate range of 0.25–0.65 kg/s. Very promising results has been obtained in preliminary investigation. Heat transfer coefficient as high as 13,500 W/m2k has been obtained which is almost five times higher than comparative state of art technologies. The associated pressure drop is quite modest and much less than state of the art conventional evaporators.

Integrated Eco-Thermal Management for Aerospace

2005 ◽  
Author(s):  
Lev Reznikov
Keyword(s):  
Heat Transfer ◽  
Thermal Management ◽  
High Performance ◽  
Waste Heat ◽  
Space Station ◽  
Nucleate Boiling ◽  
High Heat ◽  
Novel Technologies ◽  
Related Substances ◽  
Nucleation Sites

Thermal Management System developed for aerospace carriers (missile, aircraft, space station), bounds processes of generation and dissipation, transfer and conversion of power, refrigeration, and of bio-metabolism related substances. Local ecosystem of the carrier combines technological and biological subsystems, interacting with internal and outer spaces. The conceptual IETM System performs recovery of waste thermal energy, generation of “free” refrigeration, and recovery of byproducts into safe coolants (ammonia - water). Thermal Management solutions include novel technologies of intensification of the heat transfer and of conversion of the waste resources into refrigeration for extension of cooling capabilities for high heat radars, lasers and microwave generators. The IETM includes Vacuum-Evaporative Refrigeration (VER) utilizing “free natural” vacuum and waste heat-activated refrigeration circuits. VER generates ~1000 Btu of “free” cold per pound of wastewater or ammonia. The introduced high performance microstructure of compound electrohydrodynamic (EHD) boundary microsystems intensifies nucleate boiling, preventing dryout. The coils of the microwires adjoin to the boiling surface and form precision microstructure of heat sink with microchannels between the coils and the surface. The microcavities form the active bubbling nucleation sites along the spiral zones of contacts of the microwires and basic surfaces. The fins-microelectrodes develop additional heat transfer surface and evenly distributed spiral zones of the nucleation sites. Like fibers of a fine wick, the electric forces in EHD capillary structures of the microelectrodes retain the liquid and push out generated vapor bubbles from the surface. Good manufacturability and performance of novel MEMS are based on well-developed materials and common winding technology “borrowed” from electrotechnical industry. Conversion of waste resources into refrigeration and EHD activation of boiling allow meeting strong limitations in weight, reliability and consumption of energy. These conceptual approaches provide diversities in refrigeration capabilities for IETM.

scholarly journals Experimental Study on Behavior of Coolants, Particularly the Oil-Cooling Method, in Electric Vehicle Motors Using Hairpin Winding

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 956
Author(s):  
Taewook Ha ◽  
Nyeon Gu Han ◽  
Min Soo Kim ◽  
Kyu Heon Rho ◽  
Dong Kyu Kim
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Management ◽  
Flow Rate ◽  
High Performance ◽  
Cooling Performance ◽  
Oil Film ◽  
Cooling Method ◽  
Motor Cooling ◽  
The Heat Transfer Coefficient

This paper analyzes the characteristics of oil behavior in the oil-cooling of motors with hairpin winding to understand how to maximize cooling performance. The oil cooling is performed by directly spraying oil onto the motor components. The results show that as the temperature of the oil increases, the viscosity decreases, and the oil film is formed more evenly; however, oil splashing also increases. Similarly, as the flow rate increases, oil splashing also increases, but the amount of oil forming the oil film increases. However, the oil film is not affected by the rotor’s rotation. In contrast, the immersed oil is found to be closely related to the rotor’s rotation. As the rotational speed increases, the immersion oil is mixed with the air, and oil churning occurs. The mixing phenomenon increases as the temperature and flow rate of the oil increases. The higher the oil level, the greater the oil churning. As the oil is mixed with air, the heat transfer coefficient decreases, which adversely affects the thermal management of the motor. As a result, when considering the oil film and the immersion oil, the optimal oil temperature, flow rate, and oil level are at 60 °C, 0.140 kg/s, and 85 mm, respectively. The results of this paper give important information about EV motor cooling and can contribute to the development of high-performance motors.

Heat Transfer and Pressure Drop in a Converging Pedestal Array With Exit Area Variation

2018 ◽  
Author(s):  
L. W. Soma ◽  
F. E. Ames ◽  
S. Acharya
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Rate ◽  
Film Cooling ◽  
Reynolds Numbers ◽  
Flow Path ◽  
Internal Cooling ◽  
Channel Measurements ◽  
Trailing Edge ◽  
Cooling Air

The trailing edge of a vane is one of the most difficult areas to cool due to a narrowing flow path, high external heat transfer rates, and deteriorating external film cooling protection. Converging pedestal arrays are often used as a means to provide internal cooling in this region. The thermally induced stresses in the trailing edge region of these converging arrays have been known to cause failure in the pedestals of conventional solidity arrays. The present paper documents the heat transfer and pressure drop through two high solidity converging rounded diamond pedestal arrays. These arrays have a 45 percent pedestal solidity. One array which was tested has nine rows of pedestals with an exit area in the last row consistent with the convergence. The other array has eight rows with an expanded exit in the last row to enable a higher cooling air flow rate. The expanded exit of the eight row array allows a 30% increase in the coolant flow rate compared with the nine row array for the same pressure drop. Heat transfer levels correlate well based on local Reynolds numbers but fall slightly below non converging arrays. The pressure drop across the array naturally increases toward the trailing edge with the convergence of the flow passage. A portion of the cooling air pressure drop can be attributed to acceleration while a portion can be attributed to flow path losses. Detailed array static pressure measurements provide a means to develop a correlation for the prediction of pressure drop across the cooling channel. Measurements have been acquired over Reynolds numbers based on exit flow conditions and the characteristic pedestal length scale ranging from 5000 to over 70,000.

Letterbox Trailing Edge Heat Transfer: Effects of Blowing Rate, Reynolds Number, and External Turbulence on Heat Transfer and Film Cooling Effectiveness

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
N. J. Fiala ◽  
I. Jaswal ◽  
F. E. Ames
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Flow Rate ◽  
Film Cooling ◽  
Suction Surface ◽  
Trailing Edge ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness

Heat transfer and film cooling distributions have been acquired for a vane trailing edge with letterbox partitions. Additionally, pressure drop data have been experimentally determined across a pin fin array and a trailing edge slot with letterbox partitions. The pressure drop across the array and letterbox trailing edge arrangement was measurably higher than for the gill slot geometry. Experimental data for the partitions and the inner suction surface region downstream from the slot have been acquired over a four-to-one range in vane exit condition Reynolds number (500,000, 1,000,000, and 2,000,000), with low (0.7%), grid (8.5%), and aerocombustor (13.5%) turbulence conditions. At these conditions, both heat transfer and adiabatic film cooling distributions have been documented over a range of blowing ratios (0.47≤M≤1.9). Heat transfer distributions on the inner suction surface downstream from the slot ejection were found to be dependent on both ejection flow rate and external conditions. Heat transfer on the partition side surfaces correlated with both exit Reynolds number and blowing ratio. Heat transfer on partition top surfaces largely correlated with exit Reynolds number but blowing ratio had a small effect at higher values. Generally, adiabatic film cooling levels on the inner suction surface are high but decrease near the trailing edge and provide some protection for the trailing edge. Adiabatic effectiveness levels on the partitions correlate with blowing ratio. On the partition sides adiabatic effectiveness is highest at low blowing ratios and decreases with increasing flow rate. On the partition tops adiabatic effectiveness increases with increasing blowing ratio but never exceeds the level on the sides. The present paper, together with a companion paper that documents letterbox trailing edge aerodynamics, is intended to provide engineers with the heat transfer and aerodynamic loss information needed to develop and compare competing trailing edge designs.

Improving the Hall Thruster Global Efficiency over a Wide Flow-Rate Range

2021 ◽  
pp. 1-9
Author(s):  
Hao-tian Fan ◽  
Hong Li ◽  
Wei Mao ◽  
Yong-Jie Ding ◽  
Li-Qiu Wei ◽  
...  
Keyword(s):  
Flow Rate ◽  
Hall Thruster ◽  
Rate Range ◽  
Global Efficiency ◽  
Flow Rate Range

An Analytical Study of the Optimized Performance of an Impingement Heat Sink

2004 ◽  
Vol 126 (4) ◽  
pp. 528-534 ◽  
Author(s):  
S. B. Sathe ◽  
B. G. Sammakia
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
High Performance ◽  
Cross Flow ◽  
High Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer ◽  
Flow Through

The results of a study of a new and unique high-performance air-cooled impingement heat sink are presented. An extensive numerical investigation of the heat sink performance is conducted and is verified by experimental data. The study is relevant to cooling of high-power chips and modules in air-cooled environments and applies to workstations or mainframes. In the study, a rectangular jet impinges on a set of parallel fins and then turns into cross flow. The effects of the fin thickness, gap nozzle width and fin shape on the heat transfer and pressure drop are investigated. It is found that pressure drop is reduced by cutting the fins in the central impingement zone without sacrificing the heat transfer due to a reduction in the extent of the stagnant zone. A combination of fin thicknesses of the order of 0.5 mm and channel gaps of 0.8 mm with appropriate central cutout yielded heat transfer coefficients over 1500 W/m2 K at a pressure drop of less than 100 N/m2, as is typically available in high-end workstations. A detailed study of flow-through heat sinks subject to the same constraints as the impingement heat sink showed that the flow-through heat sink could not achieve the high heat transfer coefficients at a low pressure drop.

Design Optimization of Splitter Blade Impeller in a Centrifugal Pump

2020 ◽  
Author(s):  
Shunya Takao ◽  
Kentarou Hayashi ◽  
Masahiro Miyabe
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Design Method ◽  
General Purpose ◽  
Stable Operation ◽  
Centrifugal Pumps ◽  
Unstable Flow ◽  
Rate Range ◽  
Flow Rate Range ◽  
Suction Performance

Abstract In order to improve suction performance, centrifugal pumps with an inducer are used for rocket pumps, liquid gas transport such as LNG, and general-purpose pumps. Since a higher suction performance than conventional pump is required, a splitter blade that consists of a long blade and a short blade is sometimes adopted. However, the design becomes more difficult due to the increased number of parameters. The stable operation over a wide flow rate range are required in the general-purpose pumps. Therefore it is necessary to design them so that unstable flow phenomena such as surges do not occur. However, the design method to avoid them is not well understood yet. In this study, we focused on the splitter blade impeller in a general-purpose low-speed centrifugal pump with an inducer. Six parameters such as leading edge position and trailing edge position of the short blade for both hub-side and tip-side were set as design ones. A multi-objective optimization method using a commercial software was applied to improve suction performance while maintaining high efficiency. Then obtained optimal shape were analyzed by CFD calculation and extracted the feature. Furthermore, optimized impellers were manufactured and confirmed the performance over a wide flow rate range by experiments. In addition, a optimizing design method that improves pump performance at lower cost was studied.

scholarly journals The Integrated Component-System Optimization of a Typical Thermal Management System by Combining Empirical and Heat Current Methods

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6347
Author(s):  
Junhong Hao ◽  
Youjun Zhang ◽  
Nian Xiong
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Thermal Management ◽  
Management System ◽  
Optimal Allocation ◽  
Current Method ◽  
Heat Current ◽  
Component System ◽  
Minimum Pressure ◽  
Thermal Management System

Integration of modeling and optimization of a thermal management system simultaneously depends on heat transfer performance of the components and the topological characteristics of the system. This paper introduces a heat current method to construct the overall heat current layout of a typical double-loop thermal management system. We deduce the system heat transfer matrix as the whole system constraint based on the overall heat current layout. Moreover, we consider the influences of structural and operational parameters on the thermal hydraulic performances of each heat exchanger by combining the empirical correlations of the heat transfer and pressure drop. Finally, the minimum pressure drop is obtained by solving these optimal governing equations derived by the Lagrange multiplier method considering the physical constraints and operational conditions. The optimization results show that the minimum pressure drop reduces about 8.1% with the optimal allocation of mass flow rates of each fluid. Moreover, the impact analyses of structural and operating parameters and boundary conditions on the minimum and optimal allocation present that the combined empirical correlation-heat current method is feasible and significant for achieving integrated component-system modeling and optimization.

Effect of Mass Flow Rate on Dryer Room Radiator Pressure Drop and Heat Transfer

2016 ◽  
Vol 836 ◽  
pp. 102-108
Author(s):  
Mirmanto ◽  
Emmy Dyah Sulistyowati ◽  
I Ketut Okariawan
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Electrical Power ◽  
Maximum Temperature ◽  
Inlet Temperature ◽  
Mass Flow Rates ◽  
Room Model

In the rainy season, in tropical countries, to dry stuffs is difficult. Using electrical power or fossil energy is an expensive way. Therefore, it is wise to utilize heat waste. A device that can be used for this purpose is called radiator. The effect of mass flow rate on pressure drop and heat transfer for a dryer room radiator have been experimentally investigated. The room model size was 1000 mm x 1000 mm x 1000 mm made of plywood and the overall radiator dimension was 360 mm x 220 mm x 50 mm made of copper pipes with aluminium fins. Three mass flow rates were investigated namely 12.5 g/s, 14 g/s and 16.5 g/s. The water temperature at the entrance was increased gradually and then kept at 80°C. The maximum temperature reached in the dryer room was 50°C which was at the point just above the radiator. The effect of the mass flow rate on the room temperature was insignificant, while the effect on the pressure drop was significant. Moreover, the pressure drop decreased as the inlet temperature increased. In general, the radiator is recommended to be used as the heat source in a dryer room.

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