Thermal Efficiency of Coated Fins

1962 ◽  
Vol 84 (4) ◽  
pp. 279-282 ◽  
Author(s):  
J. A. Plamondon
Keyword(s):  
Heat Transfer ◽  
Differential Equation ◽  
Temperature Profile ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Heat Transfer Characteristics ◽  
Dimensionless Parameters ◽  
Fin Efficiency ◽  
Transfer Characteristics ◽  
Thermal Emissivity

The surfaces of a fin from which heat is rejected solely by radiation may have to be coated to obtain high values of thermal emissivity. In order to determine the influence of the conductive resistance of a coating on the thermal performance of a fin, an analysis was undertaken. Two equations are derived to describe the heat-transfer characteristics of a coated fin: One, a differential equation for the temperature profile on the radiating surfaces of the coating; and two, an equation for the relative thermal performance of the fin in terms of fin efficiency. The equations are solved numerically, and the fin efficiencies are plotted as a function of two dimensionless parameters which appear in the differential equation. These efficiencies are compared with those for fins in which the conductive resistance of the coating is ignored.

Maximizing Heat Transfer Through Joint Fin Systems

2005 ◽  
Vol 128 (2) ◽  
pp. 203-206 ◽  
Author(s):  
A.-R. A. Khaled
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Performance ◽  
Critical Length ◽  
The Other ◽  
Rigid Fixation ◽  
Convection Coefficient ◽  
Heat Transfer Characteristics ◽  
Cold Side ◽  
Transfer Characteristics

Heat transfer through joint fins is modeled and analyzed analytically in this work. The terminology “joint fin systems” is used to refer to extending surfaces that are exposed to two different convective media from its both ends. It is found that heat transfer through joint fins is maximized at certain critical lengths of each portion (the receiver fin portion which faces the hot side and the sender fin portion that faces the cold side of the convective media). The critical length of each portion of joint fins is increased as the convection coefficient of the other fin portion increases. At a certain value of the thermal conductivity of the sender fin portion, the critical length for the receiver fin portion may be reduced while heat transfer is maximized. This value depends on the convection coefficient for both fin portions. Thermal performance of joint fins is increased as both thermal conductivity of the sender fin portion or its convection coefficient increases. This work shows that the design of machine components such as bolts, screws, and others can be improved to achieve favorable heat transfer characteristics in addition to its main functions such as rigid fixation properties.

Assessment of the Thermal Performance of Alternate Firing Schemes in Oxygen-Fired Glass Melting Furnaces

2003 ◽  
Author(s):  
Kris L. Jorgensen ◽  
Satish Ramadhyani ◽  
Raymond Viskanta
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Computer Model ◽  
Thermal Performance ◽  
Glass Melting ◽  
Side Wall ◽  
Shear Stresses ◽  
Heat Transfer Characteristics ◽  
Unstable Flow ◽  
Transfer Characteristics

Three firing schemes for an industrial oxygen-fired glass melting furnace were examined to determine the thermal performance and relative merits of each scheme. A comprehensive computer model was used to investigate the effects of each scheme on the combustion and heat transfer in the furnace. The three-dimensional computer model, suitable for predicting and analyzing fluid flow, combustion and heat transfer has been used to simulate the combustion space of the furnace. The turbulent flow field is obtained by solving the Favre averaged Navier-Stokes equations and using the k-ε model to calculate the turbulent shear stresses and close the equation set. The combustion model consists of a single step, irreversible, infinitely fast reaction. A mixture fraction is used to track the mixing of fuel and oxidant and thus reaction progress in this mixing limited model. An assumed shape PDF method is utilized to account for turbulent fluctuations. Radiative heat transfer in the combustion gases and between surfaces is modeled using the discrete ordinates method coupled with the weighted-sum-of-gray-gases model. The model furnace for all three firing schemes was the same size and shape, was charged from the rear end wall and was pulled from the front wall. The three schemes investigated were: 1) non-interlaced side-wall fired, 2) interlaced side-wall fired, and 3) end fired. The results show that all three arrangements provide similar thermal performance and heat transfer characteristics. However, the flow field for the non-interlaced arrangement is very complex in the region where jets from opposing walls meet at the furnace center line. This type of jet interference can lead to unstable flow, particularly at the centerline of the furnace. Unstable flow conditions can affect the heat transfer characteristics of the furnace and make the furnace difficult to operate. Conversely, the interlaced and end-fired schemes do not exhibit the jet interference seen in the non-interlaced arrangement. While the results indicate that the thermal performance of all three arrangements were similar, the possibility of jet interference suggests that an interlaced or end-fired arrangement is preferable.

Free Convection Heat Transfer Characteristics in a Melt Water Layer

1980 ◽  
Vol 102 (3) ◽  
pp. 550-556 ◽  
Author(s):  
Yin-Chao Yen
Keyword(s):  
Heat Transfer ◽  
Temperature Profile ◽  
Constant Temperature ◽  
Water Layer ◽  
Melting Rate ◽  
Rate Measurement ◽  
Heat Transfer Characteristics ◽  
Layer Depth ◽  
Onset Of Convection ◽  
Transfer Characteristics

An experimental study was conducted on the formation of a water layer containing a maximum density, its effect on the onset of convection, and the heat transfer characteristics of such a system. This water layer was formed by one-dimensional melting (either from below or above) of a cylinder of bubble-free ice. For melting from above, with a melting rate measurement, the warm plate temperature Th varied from 4.16 to 13.09°C with initial ice temperatures T0 of −6.5 and −13°C, respectively. For experiments with a measurement of temperature profile, Th varied from 11.75 to 39.90°C with T0 at −12 and −15°C. For melting from below with a melting rate measurement, Th ranged from 7.70 to 25.50°C with four T0’s from −4.8 to −22°C. The layer depth at the onset of convection was determined by locating the inflection point on the water layer depth versus time curve, and was compared with layer depth calculated from a linear stability analysis of an identical problem. The results were compared with the analytical work of Veronis and were found to be in excellent agreement. Formation of a constant temperature layer was observed by measuring the water temperature distribution as melting progressed. The constant temperature was found to be dependent on Th for melting from below but was a constant for melting from above. The heat flux to the melting surface increased linearly with Th for melting from below, but had a weaker dependence for melting from above. Non-dimensional mean temperature profiles of the water layer were found to be in good agreement with those by Adrian for melting from above. In the case of melting from below, the mean temperature profile also fell into a single line with a somewhat higher value in the convection layer.

Numerical Study on the Flow and Heat Transfer Characteristics in Rectangular Channels With Grooves and Different Protrusions

2017 ◽  
Author(s):  
Feng Zhang ◽  
Xinjun Wang ◽  
Jun Li ◽  
Daren Zheng ◽  
Junfei Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Rectangular Channels

The present work represents a numerical study on the flow and heat transfer characteristics in rectangular channels with protrusion-grooved turbulators. The Reynolds averaged Navier-Stokes equations, coupled with SST turbulence model, are adopted and solved. In this paper, six geometric protrusion shapes (circular, rectangular, triangular, trapezoidal, circular with leading round concave and circular with trailing round concave) are selected to perform the study. The flow structure, heat transfer enhancement, friction factor as well as thermal performance factor of the rectangular channel fitted with combined groove and different protrusions have been obtained at the Reynolds number ranging from 5000 to 20000. The results indicate that the protrusion shapes affect the velocity distribution near the groove surface. The case of circular protrusion with leading round concave provides the highest overall heat transfer enhancement, while it also causes the highest pressure loss penalty. The case of rectangular protrusion has the lowest overall heat transfer enhancement with high pressure loss penalty. The case of circular protrusion has similar overall heat transfer enhancement with cases of trapezoidal protrusion as well as circular protrusion with trailing round concave, but the pressure loss penalty of the case of circular protrusion is the lowest. In addition, the best overall thermal performance can be observed for circular protrusion-grooved channel.

Effect of Wick Characteristics on the Thermal Performance of the Miniature Loop Heat Pipe

2009 ◽  
Vol 131 (8) ◽  
Author(s):  
Randeep Singh ◽  
Aliakbar Akbarzadeh ◽  
Masataka Mochizuki
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Working Fluid ◽  
Vapor Flow ◽  
Loop Heat Pipe ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Two phase heat transfer devices based on the miniature version of loop heat pipe (LHP) can provide very promising cooling solutions for the compact electronic devices due to their high heat flux management capability and long distance heat transfer with minimal temperature losses. This paper discusses the effect of the wick properties on the heat transfer characteristics of the miniature LHP. The miniature model of the LHP with disk-shaped evaporator, 10 mm thick and 30 mm disk diameter, was designed using copper containment vessel and water as the working fluid, which is the most acceptable combination in electronic cooling applications. In the investigation, wick structures with different physical properties including thermal conductivity, pore radius, porosity, and permeability and with different structural topology including monoporous or biporous evaporating face were used. It was experimentally observed that copper wicks are able to provide superior thermal performance than nickel wicks, particularly for low to moderate heat loads due to their low heat conducting resistance. With monoporous copper wick, maximum evaporator heat transfer coefficient (hev) of 26,270 W/m2 K and evaporator thermal resistance (Rev) of 0.06–0.10°C/W were achieved. For monoporous nickel wick, the corresponding values were 20,700 W/m2 K for hev and 0.08–0.21°C/W for Rev. Capillary structure with smaller pore size, high porosity, and high permeability showed better heat transfer characteristics due to sufficient capillary pumping capability, low heat leaks from evaporator to compensation chamber and larger surface area to volume ratio for heat exchange. In addition to this, biporous copper wick structure showed much higher heat transfer coefficient of 83,787 W/m2 K than monoporous copper wick due to improved evaporative heat transfer at wick wall interface and separated liquid and vapor flow pores. The present work was able to classify the importance of the wick properties in the improvement of the thermal characteristics for miniature loop heat pipes.

scholarly journals Enhancement of Heat Transfer Characteristics of Plain Fin Coated with Brass and Aluminium

2019 ◽  
Vol 8 (4) ◽  
pp. 6030-6035
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Nusselt Number ◽  
Power Plants ◽  
Heat Transfer Characteristics ◽  
Thermal Systems ◽  
Air Conditioners ◽  
Fin Efficiency ◽  
Pin Fin ◽  
Transfer Characteristics

Rate of heat transfer plays a very important role in the performance of thermal systems like heat engines, steam power plants, refrigerators, air conditioners etc. Continuous efforts are being made to improve the effectiveness of the mentioned systems. Thermal conductivity of material effects the heat transfer characteristics the most and can be enhanced by surface coating of various materials. Materials with high thermal conductivity are preferable for providing coating on substrate to improve heat transfer rate. In present work, fins made of Stainless Steel 304 coated with Brass and Aluminum (250 micrometers thickness) by Twin wire arc coating process, is investigated. Experiments were conducted with and without coating at different heat input using Pin Fin Apparatus and calculated Nusselt number, Reynolds number, thermal conductivity, heat transfer coefficient, fin efficiency. From the results obtained, it is concluded that Nusselt number in case of S.S coated with Aluminium is increased by 1.36% compared with coated with brass and 2.1% compared without coating and there is an increase in efficiency of fin coated brass and Aluminium materials by 14-73% compared to without coating.

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