Short penetration models for direct and indirect contact, co-current heat transfer

1975 ◽  
Vol 53 (4) ◽  
pp. 453-455 ◽  
Author(s):  
R. G. Rice ◽  
R. J. Marshall
Keyword(s):  
Heat Transfer ◽  
Indirect Contact ◽  
Current Heat

Numerical Simulation of Bubble Growth During Nanofluid Flow Boiling in a Microchannel

2014 ◽  
Author(s):  
Arman Khalighi ◽  
Matthew Blomquist ◽  
Abhijit Mukherjee
Keyword(s):  
Heat Transfer ◽  
Physical Properties ◽  
Heat Dissipation ◽  
Flow Boiling ◽  
Contact Angles ◽  
Electronic Systems ◽  
Simulation Based ◽  
Fluid Media ◽  
Thermo Physical Properties ◽  
Current Heat

In recent years, heat dissipation in micro-electronic systems has become a significant design limitation for many component manufactures. As electronic devices become smaller, the amount of heat generation per unit area increases significantly. Current heat dissipation systems have implemented forced convection with both air and fluid media. However, nanofluids may present an advantageous and ideal cooling solution. In the present study, a model has been developed to estimate the enhancement of the heat transfer when nanoparticles are added to a base fluid, in a single microchannel. The model assumes a homogeneous nanofluid mixture, with thermo-physical properties based on previous experimental and simulation based data. The effect of nanofluid concentration on the dynamics of the bubble has been simulated. The results show the change in bubble contact angles due to deposition of the nanoparticles has more effect on the wall heat transfer compared to the effect of thermo-physical properties change by using nanofluid.

A Novel Gas-Water Heat Exchanger With Minichannels

2008 ◽  
Author(s):  
Yang Chen ◽  
Per Lundqvist ◽  
Bjo¨rn Palm
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Low Pressure ◽  
Shell Side ◽  
Hot Air ◽  
Drop Flow ◽  
Counter Current ◽  
Good Heat ◽  
Current Heat

In the current study, a novel gas water heat exchanger with minichannels is designed, built and tested. The heat exchanger is mainly composed of a number of concentric ring shaped plates, which are made up of several heat exchanger tubes. The ring shaped plates are arranged in parallel and placed in a shell. The heat exchanger is designed as a counter current heat exchanger with laminar flow on the heat exchanger’s shell-side (gas side) and therefore has a very low pressure drop on the shell side. The heat exchanger was tested with water and hot air on its tube-side and shell-side respectively. All the necessary parameters like inlet and outlet temperatures on tube-side and shell-side as well as the pressure drop, flow rate of fluids, etc. were measured. Different existing correlations were used to calculate the overall heat transfer coefficient and the results were compared with the measured value. The measured results show that the new designed heat exchanger can achieve a good heat transfer performance and also maintain a low pressure drop on shell-side (gas side).

Assessment of Heat Transfer Effectiveness: Application to Shell Bitumen Plant, Takoradi, Ghana

2008 ◽  
Author(s):  
Anthony Simons ◽  
Solomon Nunoo
Keyword(s):  
Heat Transfer ◽  
Heat Losses ◽  
Heat Energy ◽  
Fuel Oil ◽  
High Rate ◽  
Liquefied Petroleum Gas ◽  
Temperature Range ◽  
The Face ◽  
Selection Of ◽  
Current Heat

At Shell Bitumen Plant, Takoradi, Beverley Thermal Fluid Heater (BTFH) generates heat energy to heat thermal fluid (Thermia B) which flows through heat exchanger and then heats bitumen which is to be maintained at temperature range of 140 °C to 160 °C before it is discharged. High rate of heat losses have been observed and in order to maintain the temperature range of bitumen at (140 °C to 160 °C), a lot of heat energy is needed to be generated which means higher fuel consumption for BTFH. Industrial fuel oil is used to fuel the BTFH. This paper assesses the existing insulation system on the plant and seeks to improve on it so as to cut down heat losses. Consequently, the work looked at the estimation of heat losses, selection of materials for heat transfer and lagging purposes. In this wise, the existing laggings were modified by introducing fibreglass between the asbestos and masonry and thus reducing the current heat lost by 78%. Heat from the exhaust gas which would have otherwise, gone wasted, was utilised by redesigning the chimney and this yielded 0.868 kW of heat energy to aid the heating of the bitumen. In the face of rising cost of fuel and taking cognizance of the fact that cheaper natural gas and liquefied petroleum gas could be produced in Ghana, it is recommended that the heater should be fueled by either of these gases.

Poisson Conduction Shape Factors for “Mixed Case” Counter-Current Heat Transfer Applications

2004 ◽  
Author(s):  
Devashish Shrivastava ◽  
Robert B. Roemer
Keyword(s):  
Heat Transfer ◽  
Vessel Wall ◽  
Source Term ◽  
The Other ◽  
Tissue Temperature ◽  
Shape Factors ◽  
Mixed Case ◽  
Boundary Temperature ◽  
Counter Current ◽  
Current Heat

The effects of a source term and geometry on vessel-vessel and vessel-tissue Poisson conduction shape factors (VVPCSFs and VTPCSFs) are studied for uniformly heated, finite, non-insulated tissues for the ‘mixed case’ i.e., when the tissue boundary temperature lies in between the two vessel wall temperatures. In addition, two alternative formulations for the VTPCSFs are compared; while both formulations use the vessel wall temperature, one uses the tissue boundary temperature, and the other the area averaged tissue temperature. Results show that the VVPCSFs are only geometry dependent and do not depend on the applied power or the two vessel wall and tissue boundary temperatures. Conversely, the VTPCSFs are strong functions of these variables.

A Review of Staggered Array Pin Fin Heat Transfer for Turbine Cooling Applications

1988 ◽  
Vol 110 (1) ◽  
pp. 94-103 ◽  
Author(s):  
J. Armstrong ◽  
D. Winstanley
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Geometric Parameters ◽  
Flow Friction ◽  
Turbine Cooling ◽  
Pin Fin ◽  
Pin Fins ◽  
Accelerating Flow ◽  
Correlation Accuracy ◽  
Current Heat

A review of heat transfer and flow friction data for staggered arrays of pin fins in turbine cooling applications is presented. This review presents discussions on local-and array-averaged heat transfer, the effects of different geometric parameters such as pin height and pin spacing on heat transfer and flow friction, and the effect of the accelerating flow in converging pin fin channels. A review of current heat transfer correlations is also presented with recommendations for correlating parameter limits and correlation accuracy. The correlations currently available for friction factor are reviewed, with an attempt to account for the effects of the converging channels.

A numerical analysis of heat transfer in a cross-current heat exchanger with controlled and newly designed air flows

2018 ◽  
Vol 16 (1) ◽  
pp. 627-636 ◽  
Author(s):  
Witold Żukowski ◽  
Przemysław Migas ◽  
Monika Gwadera ◽  
Barbara Larwa ◽  
Stanisław Kandafer
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Flow Resistance ◽  
Substantial Part ◽  
Fluidised Bed ◽  
Air Chamber ◽  
Model Variant ◽  
Counter Current ◽  
Cross Current ◽  
Current Heat

AbstractSimulations of heat transfer between air and flue gases in a plate heat exchanger are presented. The device was designed for the heating of the air supplying a fluidised furnace for the combustion of wet sludge and wood crumbs. The locations of inlets and outlets and the geometry of the heat exchanger are determined by the construction of the furnace. The aim of the simulations was to increase effectiveness of heat transfer through the use of flow redirections with additional baffles placed in the air chamber. The results of the simulations showed that a substantial part of the heat exchanger without baffles is not used effectively. On the basis of a velocity profile, a temperature distribution and a wall heat flux, the geometry of the inter-plate space within the air chamber was modified by adding baffles. The unmodified exchangers had 77% efficiency in comparison to counter-current exchangers with the same heat transfer area. After the application of baffles, the efficiency increased to 83-91% depending on the construction used (one, two or three baffles). The best model variant of the exchanger with baffles led to the increase in the temperature of air supplying the fluidised bed by approximately 76 K in relation to the system without baffles . Unexpectedly, the presented modifications of the geometry of the system had very low influence of the flow resistance in the air chamber. The value of Δp for the system without baffles is almost the same as for the best model variant.

Vascular Anatomy of the Counter-Current Heat Exchanger of Skipjack Tuna

1974 ◽  
Vol 61 (1) ◽  
pp. 145-153 ◽  
Author(s):  
E. DON STEVENS ◽  
HOW MAN LAM ◽  
J. KENDALL
Keyword(s):  
Heat Transfer ◽  
Blood Flow ◽  
Heat Exchanger ◽  
Vascular Anatomy ◽  
Dorsal Aorta ◽  
Gas Transfer ◽  
Skipjack Tuna ◽  
Cardinal Vein ◽  
Counter Current ◽  
Current Heat

1. The anatomy of the counter-current heat exchanger of skipjack tuna is described and the pattern of blood flow is analysed. 2. The pattern of blood flow is from the dorsal aorta, through the exchanger to segmental arteries to the tissues, from the tissues to segmental veins and back through the exchanger to the post-cardinal vein. 3. The vessels in the exchanger are about the same size as systemic arterioles and venules and are about 10 mm long. There are about 125000 of each type in a 2 kg tuna. 4. The velocity of blood flow in the exchanger is about 1/80th of that in the dorsal aorta and post-cardinal vein allowing time for heat transfer. 5. There are many valves in the segmental veins which may be expected because of the resistance offered by the exchanger. 6. The vessels in the tuna heat exchanger are an order of magnitude larger than those in the swim-bladder rete, thus permitting heat transfer but preventing gas transfer.

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