An Analytical Model for Turbulent Compression-Driven Heat Transfer

1998 ◽  
Vol 120 (3) ◽  
pp. 617-623 ◽  
Author(s):  
F. J. Cantelmi ◽  
D. Gedeon ◽  
A. A. Kornhauser
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Analytical Solution ◽  
Power Loss ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Mixing Length ◽  
Power Losses ◽  
Flow Configurations

Compression-driven heat transfer is important to the performance of many reciprocating energy-conversion machines. For small pressure variations in cylinder spaces without inflow, heat transfer and power losses are well predicted using a simple heat transfer model which neglects turbulence. In actual engine cylinders, where significant turbulence levels can be generated by high-velocity inflow, a model which neglects turbulence may not be adequate. In this paper, a heat transfer model having an analytical solution is developed for turbulent cylinder spaces based on a mixing length turbulence model. The model is then used to develop expressions for heat-transfer-related power loss and heat transfer coefficient. Predicted results compare favorably with experimental data for two in-flow configurations.

Experimental Investigation of Heat Transfer in Impingement Air Cooled Plate Fin Heat Sinks

2005 ◽  
Vol 128 (4) ◽  
pp. 412-418 ◽  
Author(s):  
Zhipeng Duan ◽  
Y. S. Muzychka
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Transfer Model ◽  
Heat Sinks ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Developing Flow ◽  
Rectangular Channels

Impingement cooling of plate fin heat sinks is examined. Experimental measurements of thermal performance were performed with four heat sinks of various impingement inlet widths, fin spacings, fin heights, and airflow velocities. The percent uncertainty in the measured thermal resistance was a maximum of 2.6% in the validation tests. Using a simple thermal resistance model based on developing laminar flow in rectangular channels, the actual mean heat transfer coefficients are obtained in order to develop a simple heat transfer model for the impingement plate fin heat sink system. The experimental results are combined into a dimensionless correlation for channel average Nusselt number Nu∼f(L*,Pr). We use a dimensionless thermal developing flow length, L*=(L∕2)∕(DhRePr), as the independent parameter. Results show that Nu∼1∕L*, similar to developing flow in parallel channels. The heat transfer model covers the practical operating range of most heat sinks, 0.01<L*<0.18. The accuracy of the heat transfer model was found to be within 11% of the experimental data taken on four heat sinks and other experimental data from the published literature at channel Reynolds numbers less than 1200. The proposed heat transfer model may be used to predict the thermal performance of impingement air cooled plate fin heat sinks for design purposes.

Isentropic Compressor Efficiency Calculation Method for Small Gasoline Engine Turbocharger Using Supplier Performance Maps

2021 ◽  
Author(s):  
Georges Salameh ◽  
Guillaume Goumy ◽  
Pascal Chesse
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Gasoline Engine ◽  
Experimental Tests ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Flow Equations ◽  
Adiabatic Flow ◽  
Efficiency Calculation ◽  
Isentropic Efficiency

Abstract A turbocharger efficiency performance map given by the supplier is calculated using adiabatic flow equations and non-adiabatic experimental data. The experimental data used for this calculation is measured in hot gas stand conditions which are not adiabatic and the efficiency calculation needs correction. This paper presents a method to correct the isentropic efficiency of a compressor using the supplier maps and a heat transfer model applied on the compressor. Water is circulating in the central housing to cool the turbocharger and this water flow could be considered as insulation for heat transfer between the compressor and the turbine. The thermal effect of the turbine on the compressor is then neglected and the compressor heat flux is calculated and used to correct the isentropic efficiency calculation. The heat transfer is considered between the compressor and the surrounding environment and between the compressor and the central housing. Experimental adiabatic measurements are used to validate the model. Experimental tests are carried with different oil and water temperatures combinations to test the accuracy of the heat transfer model with these different combinations.

Optimal Control Experimentation of Compression Trajectories for a Liquid Piston Air Compressor

2013 ◽  
Author(s):  
Farzad A. Shirazi ◽  
Mohsen Saadat ◽  
Bo Yan ◽  
Perry Y. Li ◽  
Terry W. Simon
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Power Density ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Compression Efficiency ◽  
Air Compressor ◽  
Compression Time ◽  
Liquid Piston

Air compressor is the critical part of a Compressed Air Energy Storage (CAES) system. Efficient and fast compression of air from ambient to a pressure ratio of 200–300 is a challenging problem due to the trade-off between efficiency and power density. Compression efficiency is mainly affected by the amount of heat transfer between the air and its surrounding during the compression. One way to increase heat transfer is to implement an optimal compression trajectory, i.e., a unique trajectory maximizing the compression efficiency for a given compression time and compression ratio. The main part of the heat transfer model is the convective heat transfer coefficient (h) which in general is a function of local air velocity, air density and air temperature. Depending on the model used for heat transfer, different optimal compression profiles can be achieved. Hence, a good understanding of real heat transfer between air and its surrounding wall inside the compression chamber is essential in order to calculate the correct optimal profile. A numerical optimization approach has been proposed in previous works to calculate the optimal compression profile for a general heat transfer model. While the results show a good improvement both in the lumped air model as well as Fluent CFD analysis, they have never been experimentally proved. In this work, we have implemented these optimal compression profiles in an experimental setup that contains a compression chamber with a liquid piston driven by a water pump through a flow control valve. The optimal trajectories are found and experimented for different compression times. The actual value of heat transfer coefficient is unknown in the experiment. Therefore, an iterative procedure is employed to obtain h corresponding to each compression time. The resulted efficiency versus power density of optimal profiles is then compared with ad-hoc constant flow rate profiles showing up to %4 higher efficiency in a same power density or %30 higher power density in a same efficiency in the experiment.

Analytical solution of a heat transfer model for a tubular co-current diluted moving bed reactor with indirect heating and intraparticle gradients

2019 ◽  
Vol 351 ◽  
pp. 259-272 ◽  
Author(s):  
Sávio L. Bertoli ◽  
Richard Tribess ◽  
Vitória A. Castamann ◽  
Aline Lovatel ◽  
Carolina K. de Souza
Keyword(s):  
Heat Transfer ◽  
Analytical Solution ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Moving Bed ◽  
Indirect Heating

A Heat Transfer Model Based on Finite Difference Method for Grinding

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Bin Shen ◽  
Albert J. Shih ◽  
Guoxian Xiao
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Boundary Conditions ◽  
Contact Zone ◽  
Convection Heat Transfer ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Convection Heat ◽  
Convection Heat Transfer Coefficient ◽  
Mql Grinding

A heat transfer model for grinding has been developed based on the finite difference method (FDM). The proposed model can solve transient heat transfer problems in grinding, and has the flexibility to deal with different boundary conditions. The model is first validated by comparing it with the traditional heat transfer model for grinding which assumes the semiinfinite workpiece size and adiabatic boundary conditions. Then it was used to investigate the effects of workpiece size, feed rate, and cooling boundary conditions. Simulation results show that when the workpiece is short or the feed rate is low, transient heat transfer becomes more dominant during grinding. Results also show that cooling in the grinding contact zone has much more significant impact on the reduction of workpiece temperature than that in the leading edge or trailing edge. The model is further applied to investigate the convection heat transfer at the workpiece surface in wet and minimum quantity lubrication (MQL) grinding. Based on the assumption of linearly varying convection heat transfer coefficient in the grinding contact zone, FDM model is able to calculate convection coefficient from the experimentally measured grinding temperature profile. The average convection heat transfer coefficient in the grinding contact zone was estimated as 4.2 × 105 W/m2-K for wet grinding and 2.5 × 104 W/m2-K for MQL grinding using vitrified bond CBN wheels.

scholarly journals A Heat Transfer Model for the Production of Semi-Solid Billets with the SEED Process

2006 ◽  
Vol 519-521 ◽  
pp. 1525-1532 ◽  
Author(s):  
Josée Colbert ◽  
Dominique Bouchard
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Computer Model ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Inverse Technique ◽  
Solid Aluminum ◽  
Semi Solid ◽  
The Heat Transfer Coefficient

A heat transfer model was built to predict the temperature evolution of semi-solid aluminum billets produced with the SEED process. An inverse technique was used to characterize the heat transfer coefficient at the interface between the crucible and the semi-solid billet. The effect of several process parameters on the heat transfer coefficient was investigated with a design of experiments and the coefficient was inserted in a computer model. Numerical simulations were carried out and validated with experimental results.

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