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Technical Briefs

Step Response of a Single-Pass Crossflow Heat Exchanger With Variable Inlet Temperatures and Mass Flow Rates

[+] Author and Article Information
Karthik Silaipillayarputhur

PT Indo Kordsa
Tbk, Citeureup, Indonesia 16810

Stephen A. Idem

Tennessee Tech University,
Cookeville, TN 38574

Manuscript received December 15, 2011; final manuscript received June 14, 2012; published online October 12, 2012. Assoc. Editor: Arun Muley.

J. Thermal Sci. Eng. Appl 4(4), 044501 (Oct 12, 2012) (6 pages) doi:10.1115/1.4007206 History: Received December 15, 2011; Revised June 14, 2012

The step response of a single-pass crossflow heat exchanger with variable inlet temperatures and mass flow rates was determined. In every instance, the energy balance equations were solved using an implicit central finite difference method. Numerical predictions were obtained for cases where both the minimum or maximum capacity rate fluids were subjected to step changes in inlet temperature, coupled with step mass flow rate changes of the fluids. Likewise, performance calculations were conducted for heat exchangers operating initially at steady state, where step flow rate changes of the minimum and maximum capacity rate fluids were imposed in the absence of any temperature perturbations. Because of the storage of energy in the heat exchanger wall, and finite propagation times associated with the inlet perturbations, the outlet temperatures of both fluids do not respond instantaneously. A parametric study was conducted by varying the dimensionless parameters governing the transient response of the heat exchanger over a representative range of values.

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References

Spiga, G., and Spiga, M., 1987, “Two-Dimensional Transient Solutions for Crossflow Heat Exchangers With Neither Gas Mixed,” ASME J. Heat Transfer, 109, pp. 281–286. [CrossRef]
Spiga, M., and Spiga, G., 1988, “Transient Temperature Fields in Crossflow Heat Exchangers With Finite Wall Capacitance,” ASME J. Heat Transfer, 110, pp. 49–53. [CrossRef]
Spiga, M., and Spiga, G., 1992, “Step Response of the Crossflow Heat Exchanger With Finite Wall Capacitance,” Int. J. Heat Mass Transfer, 35(2), pp. 559–565. [CrossRef]
Mishra, M., Das, P. K., and Sarangi, S., 2004, “Transient Behavior of Crossflow Heat Exchangers With Longitudinal Conduction and Axial Dispersion,” ASME J. Heat Transfer, 126, pp. 425–433. [CrossRef]
Mishra, M., Das, P. K., and Sarangi, S., 2006, “Transient Behaviour of Crossflow Heat Exchangers Due to Perturbations in Temperature and Flow, Int. J. Heat Mass Transfer, 49, pp. 1083–1089. [CrossRef]
Dwivedi, A. K., and Das, S. K., 2007, “Dynamics of Plate Heat Exchangers Subject to Flow Variations,” Int. J. Heat Mass Transfer, 50, pp. 2733–2743. [CrossRef]
Mishra, M., Das, P. K., and Sarangi, S., 2008, “Effect of Temperature and Flow Nonuniformity on Transient Behaviour of Crossflow Heat Exchanger,” Int. J. Heat Mass Transfer, 51, pp. 2583–2592. [CrossRef]
Silaipillayarputhur, K., 2010, “Development of a Steady State and Transient Sensible Performance Model for a Crossflow Heat Exchanger,” Ph.D. dissertation, Tennessee Tech University, Cookeville, TN.

Figures

Grahic Jump Location
Fig. 1

Finite difference grid in a crossflow heat exchanger

Grahic Jump Location
Fig. 2

Mean fluid exit temperature of the ‘a’ and ‘b’ fluids due to a step temperature change of the ‘a’ fluid inlet temperature; E = R = 1, V = 0, γa = γb = 1

Grahic Jump Location
Fig. 3

Mean fluid exit temperature of the ‘a’ fluid due to a step change of the ‘a’ fluid inlet temperature coupled with a step flow rate change of the ‘a’ fluid; initially E = R = V = NTU = 1; γb = 1

Grahic Jump Location
Fig. 4

Mean fluid exit temperature of the ‘b’ fluid due to a step change of the ‘a’ fluid inlet temperature coupled with a step flow rate change of the ‘a’ fluid; initially E = R = V = NTU = 1 and γb = 1

Grahic Jump Location
Fig. 5

Mean fluid exit temperature of the ‘a’ fluid due to a step change of the ‘b’ fluid inlet temperature coupled with a step flow rate change of the ‘b’ fluid; initially E = R = V = NTU = 1 and γa = 1

Grahic Jump Location
Fig. 6

Mean fluid exit temperature of the ‘b’ fluid due to a step change of the ‘b’ fluid inlet temperature coupled with a step flow rate change of the ‘b’ fluid; initially E = R = V = NTU = 1 and γa = 1

Grahic Jump Location
Fig. 7

Mean fluid exit temperature of the ‘a’ fluid due to a step change of the ‘a’ fluid flow rate in the absence of any temperature perturbation; initially E = R = V = NTU = 1 and γb = 1

Grahic Jump Location
Fig. 8

Mean fluid exit temperature of the ‘b’ fluid due to a step change of the ‘a’ fluid flow rate in the absence of any temperature perturbation; initially E = R = V = NTU = 1 and γb = 1

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