scholarly journals Performance Tests on a Novel Un-Finned Thermosyphon Heat Exchanger Requiring Single Charge

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 995
Author(s):  
Kai-Shing Yang ◽  
Yan-Lin Wu ◽  
Yi-Pin Chu ◽  
Yu-Lieh Wu ◽  
Shwin-Chung Wong
Keyword(s):  
Silicone Oil ◽  
Waste Heat ◽  
Total Error ◽  
Air Flow ◽  
Film Condensation ◽  
Single Charge ◽  
Condenser Section ◽  
Pressure Drops ◽  
Cooling Air Flow ◽  
Cooling Air

A novel design of an unfinned thermosyphon HPHX having a continuous closed tube loop which requires only a single charge is proposed for industrial waste heat recovery. The HPHX consists of 9×17 straight copper tubes in a staggered arrangement connected by 144 U bends. Without fins, not only are the pressure drops of the cooling air flow limited, but the cost, weight and maintenance effort can be greatly reduced. The thermal performance of this novel thermosyphon HPHX was tested with water at a filling ratio of 40%. The evaporator section is immersed in hot silicone oil, while the condenser section is cooled by air flow. The heat transfer rate (Q) reaches 6.65 kW at a heating pool temperature of 150 °C and a cooling air flow rate (F) of 1600 CMH, when the HPHX attains maximum effective thermal conductivity of 12,798 W/m-K. An ε-NTU theoretical model for single-tube thermosyphons was formulated with the boiling and film condensation modelled by empirical correlations. This model predicts the total resistance Rtot of the HPHX, which decreases with Q and F, with a total error of less than ±10%.

Development of Thermoelectric Conversion System for Waste Heat Recovery of Automobile Engine Exhaust Gas

2013 ◽  
Vol 284-287 ◽  
pp. 713-717 ◽  
Author(s):  
Tzer Ming Jeng ◽  
Sheng Chung Tzeng
Keyword(s):  
Thermoelectric Generator ◽  
Engine Speed ◽  
Waste Heat ◽  
Air Flow ◽  
Energy Output ◽  
Thermoelectric Conversion ◽  
External Cooling ◽  
Conversion System ◽  
Cooling Air Flow ◽  
Cooling Air

In the viewpoint of energy reutilization, this study combined high efficiency heat transfer with thermoelectric conversion technology to construct an efficiency testing platform for the waste heat recovering thermoelectric conversion system for real vehicles. A Toyota 2200c.c. vehicle with four-cylinder four-cycle engine was used for vehicle test to discuss the influence of the vehicle's engine speed and external cooling air flow on the energy output of the waste heat recovering thermoelectric conversion system. This study found that the energy output increases with the engine speed. However, if the engine speed is too high (exceeding 2500rpm), the thermoelectric generator can be overheated and damaged, which should be avoided. In addition, there is an optimal external cooling air flow generating the maximum energy output. The optimal external cooling air flow is 0.04 m3/sec in this study. At present, the 6 thermoelectric generator modules connected in series have the maximum electric power (P) output about 16W when the blowing air flow is 0.04 m3/sec and the engine speed is 2500 rpm.

TECHNICAL DEVELOPMENT OF HEAT ENERGY RECOVERY FOR VEHICLE POWER SYSTEM

2013 ◽  
Vol 37 (3) ◽  
pp. 885-894 ◽  
Author(s):  
Tzer-Ming Jeng ◽  
Sheng-Chung Tzeng
Keyword(s):  
Engine Speed ◽  
Waste Heat ◽  
Air Flow ◽  
Maximum Energy ◽  
Energy Output ◽  
External Cooling ◽  
Vehicle Test ◽  
Cooling Air Flow ◽  
Heat Energy Recovery ◽  
Cooling Air

A Toyota 2200 c.c. vehicle with four-cylinder four-cycle engine was used for real vehicle test to discuss the influence of the vehicle’s engine speed and external cooling air flow on the energy output of the waste heat recovering thermoelectric conversion system. This study found that the energy output increased with the engine speed. However, if the engine speed was too high (exceeding 2500 rpm), the thermoelectric generator would be overheated and damaged. Besides, there was an optimal external cooling air flow to generate the maximum energy output.

Analysis of Effect of Advanced Technique Configurations on Overall Performance of High Bypass Turbofan Engine

2014 ◽  
Author(s):  
Liu Jian Jun
Keyword(s):  
Air Flow ◽  
Engine Performance ◽  
Performance Model ◽  
Direct Drive ◽  
Nozzle Throat ◽  
Advanced Technique ◽  
Turbofan Engine ◽  
Overall Performance ◽  
Cooling Air Flow ◽  
Cooling Air

An analytical study was undertaken using the performance model of a two spool direct drive high BPR 300kN thrust turbofan engine, to investigate the effects of advanced configurations on overall engine performance. These include variable bypass nozzle, variable cooling air flow and more electric technique. For variable bypass nozzle, analysis on performance of outer fan at different conditions indicates that different operating points cannot meet optimal performance at the same time if the bypass nozzle area kept a constant. By changing bypass nozzle throat area at different states, outer fan operating point moves to the location where airflow and efficiency are more appropriate, and have enough margin away from surge line. As a result, the range of variable area of bypass nozzle throat is determined which ensures engine having a low SFC and adequate stability. For variable cooling airflow, configuration of turbine cooling air flow extraction and methodology for obtaining change of cooling airflow are investigated. Then, base on temperature analysis of turbine vane and blade and resistance of cooling airflow, reduction of cooling airflow is determined. Finally, using performance model which considering effect of cooling air flow on work and efficiency of turbine, variable cooling airflow effect on overall performance is analyzed. For more electric technique, the main characteristic is to use power off-take instead of overboard air extraction. Power off-take and air extraction effect on overall performance of high bypass turbofan engine is compared. Investigation demonstrates that power offtake will have less SFC.

The Effect of Fill Volume on Heat Transfer From Air-Cooled Thermosyphons

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Christina A. Pappas ◽  
Paul M. De Cecchis ◽  
Donald A. Jordan ◽  
Pamela M. Norris
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Air Flow ◽  
Condenser Section ◽  
Evaporator Temperature ◽  
Evaporator Section ◽  
Fill Volume ◽  
Inner Diameter ◽  
Cooling Air Flow

The effect of fill volume on the heat transfer performance of a cylindrical thermosyphon with an aspect ratio (ratio of the length of the evaporator section to the inner diameter) of 2.33 immersed in a cooling air flow is investigated. The fill volume was systematically varied from 0% to 70.3% of the volume of the evaporator section in a copper-water thermosyphon having an inner diameter of 19 mm. The condenser section was immersed in a uniform air flow in the test section of an open return wind tunnel. The heat transfer rate was measured as a function of evaporator temperature and fill volume, and these results were characterized by three distinct regions. From 0% to roughly 16% fill volume (Region I), the low rate of heat transfer, which is insensitive to fill volume, suggests that dry out may be occurring. In Region II (extending to approximately 58% fill volume), the heat transfer rate increases approximately linearly with fill volume, and increasing evaporator temperature results in decreased rate of heat transfer. Finally, in Region III (from roughly 58–70.3%), the rate of heat transfer increases more rapidly, though still linearly, with fill volume, and increasing evaporator temperature results in increased rate of heat transfer. The thermosyphon rate of heat transfer is greatest at 70.3% fill volume for every evaporator temperature.

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