Heat Transfer in a Long, Thin Tube Section of an Air Compressor: An Empirical Correlation From CFD and a Thermodynamic Modeling

2012 ◽  
Author(s):  
Chao Zhang ◽  
Mohsen Saadat ◽  
Perry Y. Li ◽  
Terrence W. Simon
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Flow Rate ◽  
Dimensionless Number ◽  
Transfer Model ◽  
Heat Flow Rate ◽  
Air Compressor ◽  
Thin Tube ◽  
Linear Ode ◽  
Liquid Piston

Heat transfer during compression of air in a long, thin tube is studied by CFD. The tube represents one of the many in a honeycomb geometry inserted in a liquid piston air compressor to minimize temperature rise. A dimensionless number for the heat flow rate that includes the changing heat transfer area between the tube wall and air during compression is used. From the CFD results, alinear relation between the inverse of this dimensionless heat flow rate and the Stanton number is found. Using thisrelation, the transient volume-averaged temperature, and heat flow rate from the air can be well predicted by thermodynamic modeling.With the heat transfer model, a non-linear ODE is solved numerically todetermine the average temperature and pressure. The application of this study can be found in liquid piston air compressors for compressed air energy storage systems.

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.

Effect of heat generation and thermal radiation on heat transfer in porous enclosure having t-shape inner geometry

2020 ◽  
pp. 095440892097311
Author(s):  
Pentyala Srinivasa Rao ◽  
Anil Kumar
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Thermal Radiation ◽  
Viscous Dissipation ◽  
Flow Rate ◽  
Heat Flow Rate ◽  
Radiation Parameter ◽  
Average Heat ◽  
Dissipation Parameter ◽  
Porous Enclosure

The numerical investigation of steady two-dimensional free convection is conducted to analyze the thermal radiation and viscous dissipation effects on heat transfer characteristics in fluid saturated T-shape porous hollow enclosure. The nonlinear partial differential equations in terms of stream function, using Darcy’s law and Boussinesq approximation, are solved numerically using finite difference scheme based on Gauss-Seidel approach. The results of this analysis discussed for the wide range of pertinent parameters such as radiation parameter ([Formula: see text]), viscous dissipation parameter ([Formula: see text]) and Rayleigh number ([Formula: see text]) in terms of local and average heat flow rate, streamlines and isotherms. The obtained results show that the average heat flow rate is enhanced with radiation parameter and reduced with viscous dissipation parameter. The results are graphically depicted to show the implications of the pertinent parameters in heat and flow field inside the hollow porous enclosure.

scholarly journals Heat Transfer and Friction Factor Characteristics of Heat Exchanger using Aluminium Oxide and Titanium Oxide

2019 ◽  
Vol 8 (3) ◽  
pp. 2950-2952
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Flow ◽  
Titanium Oxide ◽  
Flow Rate ◽  
Liquid Flow ◽  
Aluminium Oxide ◽  
Plain Water ◽  
Heat Flow Rate ◽  
Nano Fluids

t A heat flow and fluid flow investigation of double tube heat exchanger by means of warped tape insert under the mixing water based nano fluids. In this article Aluminium oxide and Titanium oxide was used to get better performance heat exchanging device. A different mass flow rate of fluids used to conduct the experiment and gathered various surface temperature for analyses the heat flow augmentation. A heat flow rate Nano fluids 10 to 12% was enhanced compare with the plain base water. A heat flow with liquid flow Aluminum oxide was enhanced with +8% compare with the plain base water. A heat transfer characteristics titanium oxide were augment with raise of Re and 12% was augmented compare with the plain water. However heat flow and liquid flow heat exchanging device was increasing with volume of Nano fluids increased and leading to friction facto

scholarly journals A simplified method to evaluate geothermal storage in an aquifer with consideration of heat transfer between aquifer and caprock/baserock

2020 ◽  
Vol 205 ◽  
pp. 07007
Author(s):  
Alp Cinar ◽  
Xiang Sun ◽  
Kenichi Soga ◽  
Xiaoyu Lu ◽  
Peter Nico ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Heat Loss ◽  
Flow Rate ◽  
Performance Optimization ◽  
Numerical Models ◽  
Closed Form Solution ◽  
Heat Flow Rate ◽  
Fast Evaluation ◽  
Efficient Operation

Storing and extracting heat during different seasons of the year is possible through the utilization of a ground aquifer with an open loop Ground Source Heat Pump (GSHP) system. Being able to predict the hydrothermal performance of geothermal storage is required for an efficient operation of the system for cooling and heating of buildings. Complex 2D and 3D hydrothermal numerical models can simulate the thermal performance of geothermal storage accurately but often lack the desired computational speed for conducting large number of simulations for performance optimization. Instead, a 1D radial model can be used to conduct fast evaluation. However, it is important that the model computes the amount of heat loss from an aquifer into the overburden and underlying layers accurately to evaluate the amount of geothermal storage in the aquifer at different times. In this study, a source term is introduced into a 1D model to simulate the heat transfer between the aquifer and caprock/baserock in the vertical direction. The following two heat loss models are introduced in the heat advection-conduction equation: (i) Newton’s heating/cooling law, which leads to a closed form solution, and (ii) a conduction-based semi-analytical model, which requires a 1D finite element solution. When compared to a full 2D axisymmetric simulation result, it was found that the Newton’s heating/cooling law model with a constant heat transfer coefficient works well in cases of fast heat flow rate in thick aquifers of around 100 meters. But large errors in estimating heat dissipation are observed in cases with low heat flow rate in thin aquifers, especially for simulations exceeding two to five years. On the other hand, the model with the conduction-based semi-analytical solution gives a better match for these conditions.

Measurement and Modeling of Condensation Heat Transfer Coefficients in Circular Microchannels

2006 ◽  
Vol 128 (10) ◽  
pp. 1050-1059 ◽  
Author(s):  
Todd M. Bandhauer ◽  
Akhil Agarwal ◽  
Srinivas Garimella
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Heat Transfer Model ◽  
Condensation Heat Transfer ◽  
Low Flow ◽  
Transfer Model ◽  
Shear Stresses ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Circular Microchannels

A model for predicting heat transfer during condensation of refrigerant R134a in horizontal microchannels is presented. The thermal amplification technique is used to measure condensation heat transfer coefficients accurately over small increments of refrigerant quality across the vapor-liquid dome (0<x<1). A combination of a high flow rate closed loop primary coolant and a low flow rate open loop secondary coolant ensures the accurate measurement of the small heat duties in these microchannels and the deduction of condensation heat transfer coefficients from measured UA values. Measurements were conducted for three circular microchannels (0.506<Dh<1.524mm) over the mass flux range 150<G<750kg∕m2s. Results from previous work by the authors on condensation flow mechanisms in microchannel geometries were used to interpret the results based on the applicable flow regimes. The heat transfer model is based on the approach originally developed by Traviss, D. P., Rohsenow, W. M., and Baron, A. B., 1973, “Forced-Convection Condensation Inside Tubes: A Heat Transfer Equation For Condenser Design,” ASHRAE Trans., 79(1), pp. 157–165 and Moser, K. W., Webb, R. L., and Na, B., 1998, “A New Equivalent Reynolds Number Model for Condensation in Smooth Tubes,” ASME, J. Heat Transfer, 120(2), pp. 410–417. The multiple-flow-regime model of Garimella, S., Agarwal, A., and Killion, J. D., 2005, “Condensation Pressure Drop in Circular Microchannels,” Heat Transfer Eng., 26(3), pp. 1–8 for predicting condensation pressure drops in microchannels is used to predict the pertinent interfacial shear stresses required in this heat transfer model. The resulting heat transfer model predicts 86% of the data within ±20%.

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