Effects of Nonuniform Passages on Compact Heat Exchanger Performance

1980 ◽  
Vol 102 (3) ◽  
pp. 653-659 ◽  
Author(s):  
R. K. Shah ◽  
A. L. London
Keyword(s):  
Heat Exchanger ◽  
Laminar Flow ◽  
Heat Transfer Performance ◽  
Compact Heat Exchanger ◽  
Reduced Pressure ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
Special Cases ◽  
Longitudinal Wall ◽  
Manufacturing Tolerances

Neighboring passages in a compact heat exchanger such as a rotary regenerator are never geometrically identical due to manufacturing tolerances. This passage-to-passage nonuniformity can result in a significant penalty on heat transfer performance with only a small compensating effect of reduced pressure drop. Continuous cylindrical passage geometries, operating with laminar flow, are particularly sensitive to these effects. In this paper, a procedure is outlined to establish the effective friction factors and Nusselt numbers for one fluid side of an exchanger having n different cylindrical passage geometries. Two special cases of longitudinal wall temperature variation are considered corresponding to conditions of Cmin/Cmax of zero and unity. The analysis is presented for both fully developed and developing laminar flow.

The Single-Blow Transient Testing Technique for Compact Heat Exchanger Surfaces

1967 ◽  
Vol 89 (1) ◽  
pp. 29-38 ◽  
Author(s):  
P. F. Pucci ◽  
C. P. Howard ◽  
C. H. Piersall
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Performance ◽  
Compact Heat Exchanger ◽  
Experimental Facility ◽  
Nickel Plate ◽  
Heat Transfer Characteristics ◽  
Power Penalty ◽  
Testing Technique ◽  
Flow Friction

The single-blow, transient testing technique for determining the heat transfer characteristics of heat exchanger surfaces, with a summary of the underlying theory, a description of an experimental facility, and comments on the applicability of the technique, are presented. Heat transfer and flow friction data are presented for plate-fin type surfaces fabricated of perforated nickel plate. The data indicate that perforations increase heat transfer performance without a large frictional power penalty.

Numerical Modeling of Conjugate Heat Transfer on Complex Geometries With Diagonal Cartesian Method, Part II: Applications

1999 ◽  
Vol 121 (2) ◽  
pp. 261-267 ◽  
Author(s):  
K. D. Carlson ◽  
W. L. Lin ◽  
C.-J. Chen
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Conjugate Heat Transfer ◽  
Complex Geometries ◽  
Compact Heat Exchanger ◽  
Temperature Analysis ◽  
Heat Transfer Characteristics ◽  
Reduced Pressure ◽  
Diagonal Cartesian Method

Part I of this study discusses the diagonal Cartesian method for temperature analysis. The application of this method to the analysis of flow and conjugate heat transfer in a compact heat exchanger is given in Part II. In addition to a regular (i.e., Cartesian-oriented) fin arrangement, two complex fin arrangements are modeled using the diagonal Cartesian method. The pressure drop and heat transfer characteristics of the different configurations are compared. It is found that enhanced heat transfer and reduced pressure drop can be obtained with the modified fin arrangements for this compact heat exchanger.

The Periodic Method for Testing Compact Heat Exchanger Surfaces

1974 ◽  
Vol 96 (2) ◽  
pp. 87-94 ◽  
Author(s):  
J. H. Stang ◽  
J. E. Bush
Keyword(s):  
Heat Exchanger ◽  
Heat Transfer Performance ◽  
Limited Attention ◽  
Compact Heat Exchanger ◽  
Transfer Performance ◽  
Test Results ◽  
The Past ◽  
Temperature Waves ◽  
State Technique ◽  
Periodic Method

The regular periodic method for testing the heat transfer performance of heat exchanger cores is studied in detail. This method, which has received very limited attention in the past, has certain advantages over the more conventional steady-state technique. It is shown to be useful especially in testing matrix surfaces. A theoretical analysis is performed, forming the basis for the periodic method. Directions for use in the range 0.2 < Ntu < 50, an uncertainty analysis, and test results for 2.6 < Ntu < 36.6 are included. It is concluded that the periodic method has the major advantages of: a wide Ntu range, easily generated experimental temperature waves, and the accuracy of an integral technique.

scholarly journals Transition From the Turbulent to the Laminar Regime for Internal Convective Flow With Large Property Variations

1970 ◽  
Vol 92 (3) ◽  
pp. 506-512 ◽  
Author(s):  
C. W. Coon ◽  
H. C. Perkins
Keyword(s):  
Laminar Flow ◽  
Turbulent Flow ◽  
Circular Tube ◽  
Reynolds Numbers ◽  
Bulk Temperature ◽  
Heating Rates ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
High Heating ◽  
Flow Situation

The results of a primarily experimental study of the transition from turbulent flow to laminar flow as a consequence of high heating rates are presented. Results are reported for hydrodynamically fully developed, low Mach number flows of air and helium through a vertical, circular tube. The electrically heated section was 100 diameters in length; entering Reynolds numbers ranged from 1700–40,000, and maximum wall-to-bulk temperature ratios reached 4.4. As a means of predicting the occurrence of a transition from turbulent flow to laminar flow, the experimental results are compared to the acceleration parameter suggested by Moretti and Kays and to a modified form of the parameter that is appropriate to a circular tube. It is suggested that the variable property turbulent flow correlations do not provide acceptable predictions of the Nusselt number and the friction factor if the value 4μq′′G2DTcp≃1.5×10−6 based on bulk properties, is exceeded for an initially turbulent flow situation. It is further suggested that Nusselt numbers and friction factors at locations down-stream from the point xDlaminar≃(2×10−8)(Tinlet)(Reb,inlet)2TwTbmax−1 for bulk temperatures in degrees Rankine may be obtained from the laminar correlation equations even though the flow is initially turbulent.

Heat Transfer of Aluminium-Oxide Nanofluids in a Compact Heat Exchanger

2013 ◽  
Vol 465-466 ◽  
pp. 622-628
Author(s):  
Faiza Mohamed Nasir ◽  
Mohd. H. Bahari ◽  
Y. Aiman
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Performance ◽  
Superior Performance ◽  
Compact Heat Exchanger ◽  
Transfer Performance ◽  
Test Rig ◽  
Custom Made ◽  
Experimental Works ◽  
Set Up

Experimental works were conducted to investigate the effect of Al2O3 sizes and volumeconcentration on the rate of nanofluids heat transfer in a compact heat exchanger. Two sizes ofAl2O3 nanoparticle, 40 nm and 100 nm, were mixed with demineralized water at 2% and 10%volume concentrations. Sodium Lauryl Sulphate (SLS) powder was added to enhance the mixingprocess and stabilize the dispersion of the nanofluids. A custom-made closed loop test rig weredesigned, fabricated and tested for these experiments. The test rig was set-up to represent the actualapplication of the nanofluids in cooling of a compact heat exchanger. Experimental runs wereconducted which include the runs for water, 40 nm Al2O3-water and 100 nm Al2O3-water. Theresults indicate that Al2O3-water gave better heat transfer performance than water alone. Nanofluidswith 40 nm- Al2O3 gives better heat transfer performance as compared to 100 nm- Al2O3 nanofluids.The results of the current work generally indicate that nanofluids have the potential to enhance theheat transfer of a compact heat exchanger if properly designed. This superior performance of thenanofluids would only be produced if smaller diameter of nanoparticles were used (less than 100nm). No enhancement in heat transfer can be observed by using nanofluids with particle size of 100nm or at higher volume loading (more than 5%).

Effect of Helical Screw Tape Insertion on Heat Transfer and Pressure Drop Characteristics in a Horizontal Concentric Double Tube Heat Exchanger

2014 ◽  
Vol 541-542 ◽  
pp. 622-627
Author(s):  
A.A. Kapse ◽  
P.R. Dongarwar ◽  
R.R. Gawande
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Cold Water ◽  
Hot Water ◽  
Full Length ◽  
Tube Heat Exchanger ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
Plain Tube

In the present work, the effects of insertion of helical screw tape on heat transfer characteristics and pressure drop in a concentric double tube heat exchanger are experimentally investigated. The heat exchanger has the outer (steel) and inner (copper) tube diameters of 50 mm and 25 mm respectively. The helical screw tape of diameter 19 mm is inserted into the inner tube to increase turbulence which helped to increase the heat transfer rate. The hot water was flowed through the inner tube and cold water was flowed in annulus. The helical screw tape was inserted in 1/3rd length and full length of the tube. The experiments are based on Reynolds number at tube inlet, ranging from 10000 to 42855. The experimental results show that the average Nusselt numbers and friction factors are respectively, 1.41 and 2.08 times over the plain tube for 1/3rd length insert and 1.87 and 4.31 times over the plain tube for full length insert. Furthermore, the enhancement ratio of the helical screw tape varies between 1.03 and 1.17, 1.02 and 1.26 for 1/3rd length insert and full length insert, respectively.

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