The Effect of Gravity on Heat Transfer by Rayleigh Streaming in Pulse Tubes and Thermal Buffer Tubes

2004 ◽  
Author(s):  
Konstantin I. Matveev ◽  
Scott Backhaus ◽  
Gregory W. Swift
Keyword(s):  
Heat Transfer ◽  
Analytical Model ◽  
Thermal Energy ◽  
Heat Exchangers ◽  
Acoustic Energy ◽  
Heat Leak ◽  
Thermoacoustic Engines ◽  
Different Temperatures ◽  
Rayleigh Streaming ◽  
Streaming Flow

Thermoacoustic engines and refrigerators use the interaction between heat and sound to produce acoustic energy or to transport thermal energy. Heat leaks in thermal buffer tubes and pulse tubes, components in thermoacoustic devices that separate heat exchangers at different temperatures, reduce the efficiency of these systems. At high acoustic amplitudes, Rayleigh mass streaming can become the dominat means for undesirable heat leak. Gravity affects the streaming flow patterns and influences streaming-induced heat convection. A simplified analytical model is constructed that shows gravity can reduce the streaming heat leak dramatically.

Failure Analysis of Heat Exchangers

2021 ◽  
pp. 3-19
Author(s):  
Dusan P. Sekulic
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Failure Analysis ◽  
Thermal Energy ◽  
Solid Surface ◽  
Heat Exchangers ◽  
Heat Transfer Surface ◽  
Tubular Heat Exchanger ◽  
Erosion Corrosion ◽  
Different Temperatures

Abstract Heat exchangers are devices used to transfer thermal energy between two or more fluids, between a solid surface and a fluid, or between a solid particulate and a fluid at different temperatures. This article first addresses the causes of failures in heat exchangers. It then provides a description of heat-transfer surface area, discussing the design of the tubular heat exchanger. Next, the article discusses the processes involved in the examination of failed parts. Finally, it describes the most important types of corrosion, including uniform, galvanic, pitting, stress, and erosion corrosion.

Latent Heat Storage: Container Geometry, Enhancement Techniques, and Applications—A Review

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
S. Arunachalam
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Energy ◽  
Heat Exchangers ◽  
Phase Change Materials ◽  
Heat Storage ◽  
Low Thermal Conductivity

Energy storage helps in waste management, environmental protection, saving of fossil fuels, cost effectiveness, and sustainable growth. Phase change material (PCM) is a substance which undergoes simultaneous melting and solidification at certain temperature and pressure and can thereby absorb and release thermal energy. Phase change materials are also called thermal batteries which have the ability to store large amount of heat at fixed temperature. Effective integration of the latent heat thermal energy storage system with solar thermal collectors depends on heat storage materials and heat exchangers. The practical limitation of the latent heat thermal energy system for successful implementation in various applications is mainly from its low thermal conductivity. Low thermal conductivity leads to low heat transfer coefficient, and thereby, the phase change process is prolonged which signifies the requirement of heat transfer enhancement techniques. Typically, for salt hydrates and organic PCMs, the thermal conductivity range varies between 0.4–0.7 W/m K and 0.15–0.3 W/m K which increases the thermal resistance within phase change materials during operation, seriously affecting efficiency and thermal response. This paper reviews the different geometry of commercial heat exchangers that can be used to address the problem of low thermal conductivity, like use of fins, additives with high thermal conductivity materials like metal strips, microencapsulated PCM, composite PCM, porous metals, porous metal foam matrix, carbon nanofibers and nanotubes, etc. Finally, different solar thermal applications and potential PCMs for low-temperature thermal energy storage were also discussed.

scholarly journals HEAT TRANSFER BETWEEN AN AUTOMOTIVE EXHAUST AND THERMOELECTRIC MODULES

2018 ◽  
Vol 17 (1) ◽  
pp. 03
Author(s):  
A. L. C. Silva
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Thermal Energy ◽  
Transfer Rate ◽  
Energy Transport ◽  
Thermal Contact ◽  
Electrical Energy ◽  
Exhaust Pipe ◽  
Thermoelectric Modules ◽  
Different Temperatures

This work aimed to study the heat transfer between an exhaust pipe of a car and thermoelectric modules. Heat transfer is the energy transport that occurs when quantities of matter that have different temperatures are placed in thermal contact and can occur in 3 different modes: conduction, convection and radiation. Thermoelectrics can convert thermal energy into electrical energy and vice versa. In this work a decision was made to install the Peltier cells in the final part of the exhaust pipe, where the temperature is lower. The temperature difference was 59°C. After calculations were found the values of the heat transfer rate: by conduction 0.164 W, by convection 0.103 and radiation 0.459.

A numerical study on the internal heat leak mechanisms in a variable property three-stream heat exchanger

2021 ◽  
pp. 095765092110149
Author(s):  
Yasser Shafiei-alamooti ◽  
Ali Ashrafizadeh
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Heat Conduction ◽  
Heat Exchanger ◽  
Temperature Distribution ◽  
Heat Exchangers ◽  
Numerical Study ◽  
Internal Heat ◽  
Heat Leak ◽  
Maximum Heat

Heat leakage mechanisms need to be addressed in the thermal analysis of multi-stream heat exchangers due to their effects on the intended heat transfer between the streams. In this paper, multi-dimensional heat transfers between various fluid streams and also between the fluid and solid parts of a three-stream plate-fin heat exchanger is numerically modeled considering the variation of thermo-physical properties of both solid and fluid parts. All internal heat leak mechanisms, i.e. longitudinal heat conduction, transverse bypass through fins, and heat transfer reversal in a stream are taken into consideration. The distribution of longitudinal heat conduction along the stream’s separating plates (plates) is also explored. It is shown that the longitudinal heat conduction depends strongly on the variation of properties in some flow arrangements. For such cases, the plates experience areas with relatively low temperature, and a new longitudinal heat conduction, mainly induced by property variation, is identified and presented. This induced longitudinal conduction is close to 1% of the maximum heat exchange between the streams in this study. Another interesting result is that the longitudinal temperature distribution in the plates does not necessarily follow the temperature distribution along the nearby streams due to the entrance effects and unbalanced heat capacity rates. Numerical results show that property variations affect all of the thermal leakage phenomena and, therefore, need to be considered in the modeling and thermal analysis of multi-stream heat exchangers.

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