Calculation of Transients in a Cross-Flow Heat Exchanger

1959 ◽  
Vol 81 (1) ◽  
pp. 61-67 ◽  
Author(s):  
G. M. Dusinberre
Keyword(s):  
Heat Exchanger ◽  
Numerical Methods ◽  
Gas Turbine ◽  
Digital Computer ◽  
Computer Programming ◽  
Cross Flow ◽  
Flow Rates ◽  
Flow Heat

This paper shows how transient temperatures in a cross-flow heat exchanger may be calculated by numerical methods. Digital computer programming is considered. A gas-turbine regenerator is used as an example. In particular, methods are developed which are useful when the flow rates vary, as in the starting transient.

Consideration of Uncertainties in Compact Cross-Flow Heat Exchanger Design for Gas Turbine Engine Application

2013 ◽  
Author(s):  
Randall D. Manteufel ◽  
Daniel G. Vecera
Keyword(s):  
Fluid Flow ◽  
Heat Exchanger ◽  
Gas Turbine ◽  
Flow Rate ◽  
Cross Flow ◽  
Inlet Temperature ◽  
Fluid Flow Rate ◽  
Heat Exchanger Design ◽  
Cold Fluid ◽  
Flow Heat

Recent experimental work characterized the performance of a unique cross-flow heat exchanger design for application of cooling compressor bleed air using liquid jet fuel before it is consumed in the gas turbine combustor. The proposed design has micro-channels for liquid fuel and cools air flowing in passages created using rows of intermittent fins. The design appears well suited for aircraft applications because it is compact and light-weight. A theoretical model is reported to be in good agreement with experimental measurements using air and water, thus providing a design tool to evaluate variations in the heat exchanger dimensions. This paper presents an evaluation of the heat exchanger performance with consideration of uncertainties in both model parameters and predicted results. The evaluation of the design is proposed to be reproduced by students in a thermal-fluids design class. The heat exchanger performance is reevaluated using the effectiveness–NTU approach and shown to be consistent with the method reported in the original papers. Results show that the effectiveness is low and in the range of 20 to 30% as well as the NTU which ranges from 0.25 to 0.50 when the heat capacity ratio is near unity. The thermal resistance is dominated by the hot gas convective resistance. The uncertainties attributed to fluid properties, physical dimensions, gas pressure, and cold fluid flow rate are less significant when compared to uncertainties associated with hot fluid flow rate, hot fluid inlet temperature, cold fluid inlet temperature, and convective correlation for gas over a finned surface. The model shows which heat transfer mechanisms are most important in the performance of the heat exchanger.

scholarly journals Numerical and experimental analysis of a tube-and-fin cross-flow heat exchanger with a controlled non-uniform inflow of gas

2021 ◽  
Vol 323 ◽  
pp. 00005
Author(s):  
Tomasz Bury ◽  
Małgorzata Hanuszkiewicz-Drapała
Keyword(s):  
Heat Exchanger ◽  
Water Temperature ◽  
Experimental Test ◽  
Experimental Analysis ◽  
Cross Flow ◽  
Ansys Fluent ◽  
Flow Rates ◽  
Air Inlet ◽  
Flow Heat ◽  
The Impact

The paper presents results of numerical and experimental analyses of a fin-and-tube air-water heat exchanger. The analysed device is a one-row heat exchanger with finned elliptical tubes. The aim of the analyses is to investigate the impact of a controlled non-uniform inflow of air on the heat exchanger performance. The heat exchanger was modelled numerically using the ANSYS Fluent program. The developed model was applied to simulate the heat exchanger operation in the conditions of the uniform inflow of air. Cases of an uncontrolled non-uniform inflow of gas were investigated experimentally, using a purpose-designed test station. On the experimental test station the effect of a controlled non-uniform air inflow was also achieved by placing appropriately shaped inserts in the air inlet duct, directing the air partially to the region of the water inlet header. By controlling the gas inflow, it was possible to significantly enhance the heat exchanger performance. The results of the multivariate numerical analyses conducted for the adopted parameters of the mediums (air and water volumetric flow rates and water temperature) show that the heat exchanger performance can be improved by up to almost 5% compared to a variant with a natural non-uniform air inflow taking place in the exchanger under consideration.

Heat and Mass Transfer to Air in a Cross Flow Heat Exchanger with Surface Deluge Cooling

2016 ◽  
Vol 24 (01) ◽  
pp. 1650002 ◽  
Author(s):  
Andrea Diani ◽  
Luisa Rossetto ◽  
Roberto Dall’Olio ◽  
Daniele De Zen ◽  
Filippo Masetto
Keyword(s):  
Heat Exchanger ◽  
Heat Flow ◽  
Flow Rate ◽  
Data Center ◽  
Heat Dissipation ◽  
Cross Flow ◽  
Critical Conditions ◽  
Heat Flow Rate ◽  
External Temperature ◽  
Flow Heat

Cross flow heat exchangers, when applied to cool data center rooms, use external air (process air) to cool the air stream coming from the data center room (primary air). However, an air–air heat exchanger is not enough to cope with extreme high heat loads in critical conditions (high external temperature). Therefore, water can be sprayed in the process air to increase the heat dissipation capability (wet mode). Water evaporates, and the heat flow rate is transferred to the process air as sensible and latent heat. This paper proposes an analytical approach to predict the behavior of a cross flow heat exchanger in wet mode. The theoretical results are then compared to experimental tests carried out on a real machine in wet mode conditions. Comparisons are given in terms of calculated versus experimental heat flow rate and evaporated water mass flow rate, showing a good match between theoretical and experimental values.

Minimum Irreversibility Criteria for Heat Exchanger Configurations

1999 ◽  
Vol 121 (4) ◽  
pp. 241-246 ◽  
Author(s):  
F. E. M. Saboya ◽  
C. E. S. M. da Costa
Keyword(s):  
Heat Capacity ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Second Law Of Thermodynamics ◽  
The Other ◽  
Maximum Heat ◽  
Transfer Rates ◽  
Mass Flow Rates ◽  
Flow Heat

From the second law of thermodynamics, the concepts of irreversibility, entropy generation, and availability are applied to counterflow, parallel-flow, and cross-flow heat exchangers. In the case of the Cross-flow configuration, there are four types of heat exchangers: I) both fluids unmixed, 2) both fluids mixed, 3) fluid of maximum heat capacity rate mixed and the other unmixed, 4) fluid of minimum heat capacity rate mixed and the other unmixed. In the analysis, the heat exchangers are assumed to have a negligible pressure drop irreversibility. The Counterflow heat exchanger is compared with the other five heat exchanger types and the comparison will indicate which one has the minimum irreversibility rate. In this comparison, only the exit temperatures and the heat transfer rates of the heat exchangers are different. The other conditions (inlet temperatures, mass flow rates, number of transfer units) and the working fluids are the same in the heat exchangers.

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