Numerical Investigation of Ultra-Rich Combustion in Counter Flow Heat Exchangers

The transient and steady-state response of single pass constant-flow (concentric parallel flow, concentric counter flow) heat exchangers was investigated using a finite volume method. Heat exchanger transients initiated by both step-change and sinusoidally varying hot stream inlet temperatures were investigated. The wall separating the fluid streams was modeled by conduction with thermal mass; hence the heat exchanger transient behavior is dependent on the thermal mass of the fluid streams as well as the internal wall. The outer wall is approximated as fully insulating. The time dependent temperature profiles were investigated as a function of heat exchanger dimensionless length and dimensionless time for both fluids. It was found that the transient response of the heat exchanger is controlled by a combination of the residence time and thermal capacitance of the fluid streams, the overall heat transfer coefficient between the fluid streams, and the thermal capacitance of the internal wall.

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Comparative study of the performance of the M-cycle counter-flow and cross-flow heat exchangers for indirect evaporative cooling – Paving the path toward sustainable cooling of buildings

Energy ◽

10.1016/j.energy.2011.10.019 ◽

2011 ◽

Vol 36 (12) ◽

pp. 6790-6805 ◽

Cited By ~ 127

Author(s):

Changhong Zhan ◽

Zhiyin Duan ◽

Xudong Zhao ◽

Stefan Smith ◽

Hong Jin ◽

...

Keyword(s):

Comparative Study ◽

Heat Exchangers ◽

Evaporative Cooling ◽

Cross Flow ◽

Counter Flow ◽

Flow Heat ◽

Indirect Evaporative Cooling

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Effectiveness-NTU Relations for Heat Exchangers With Streams Having Significant Kinetic Energy Variation

Journal of Heat Transfer ◽

10.1115/1.1560154 ◽

2003 ◽

Vol 125 (2) ◽

pp. 377-387 ◽

Cited By ~ 5

Author(s):

Gregory F. Nellis

Keyword(s):

Heat Exchanger ◽

Kinetic Energy ◽

Differential Equations ◽

Heat Exchangers ◽

Parallel Flow ◽

Temperature Profiles ◽

Cryogenic Temperatures ◽

Cold Side ◽

Counter Flow ◽

Flow Heat

Effectiveness-NTU equations are derived for counter and parallel-flow heat exchangers with fluids having high velocities. In this case, the change in the kinetic energy occurring within the heat exchanger will significantly affect the temperature profiles. The effectiveness is found to depend on the usual non-dimensional variables that compare the heat exchanger conductance to the hot- and cold-side capacity rates and on four additional nondimensional quantities that reflect the magnitude and distribution of the kinetic energy on the hot and cold-sides of the heat exchanger. The governing differential equations are derived, nondimensionalized, and solved analytically for the case of an exponentially distributed kinetic energy. Graphical solutions are presented and interpreted for several cases. The solutions are applied to a particular case involving high velocities within a counter-flow heat exchanger used to produce cryogenic temperatures.

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