Transient Response Of Heat Exchanger Research Articles

Experimental characterization of dynamic heat exchanger behavior

The transient response of heat exchangers plays a significant role in the time-dependent performance of thermal management systems, particularly in resource-limited situations with high power density and fast-acting heat sources. A scaled thermal management testbed with a plate-frame heat exchanger was built to emulate a thermal subsystem. This paper describes a methodology for dynamically characterizing the behavior of a commercial, off-the-shelf plate-frame heat exchanger both experimentally and computationally. Statistical design of experiments principles was used to develop a test plan composed of 20 test cases for dynamic model validation. The dynamic performance of the heat exchanger was evaluated with a physics-based model, and statistical surrogate models were derived from the experimental results. Additionally, a lumped mass model was employed to determine the dynamic parameters of the heat exchanger using the experimental data. The model efficiently and accurately predicts the experimental results across the entire experimental exploration space. The lumped mass model predicts the transient response without using computationally expensive resources such as a full numerical, thermo-fluid dynamic solvers. This approach has significant implications for developing practical models of thermal components particularly for the field of thermal controls.

Experimental transient response of a minichannel heat exchanger with step flow variation

Heat exchangers are essential components of many systems and their use is extended to include various industrial, chemical, and automotive applications. Heat exchanger behavior affects the total performance of a thermal system. Enhancing this critical component leads to improving the system overall performance and thus its energy efficiency. Since a heat exchanger operates in conjunction with other process equipment, its evaluation under a transient condition is crucial. A transient response of heat exchangers is necessary to evaluate the exchanger performance when subjected to a change in its conditions. The scarcity of experimental data on a transient response of heat exchangers in general and minichannel exchangers in particular is the main motivation for this research. This work is an investigation of an experimental characterization of the transient response of a cross flow liquid-air heat exchanger subjected to step changes in liquid mass flow rate. Hot fluid mass flow rate step changes of 0.5, 0.8, 1.5, and 2.0 are considered and the liquid outlet temperature response time is presented. The results are compared with the limited experimental work from the literature. While the outlet temperatures of both fluids do not respond instantaneously to the step change in the primary fluid mass flow rate, the cold fluid exhibits a faster response time than that of the hot fluid. The step variation increases the Reynolds number which results in a longer hot fluid response time to reach the steady state. The outcome of this work is valuable in the design, selection, and analysis of heat exchangers. The experimental data provided in this work can be used to establish a database for future advances in research. It also provides an overview of the characteristic behavior of certain parameters such as fluid temperatures, response time, and residence time when the heat exchanger is subjected to a change in the hot fluid mass flow rate.

Transfer Behavior of Heat Exchanger

This study deals with the transient response of heat exchanger which is approximated to the first-order system with delay. This function is of simple form and easy to be applied to design the practical controllers. The parameters such as gain K, time constant T and delay time are derived in this paper. On the basis of using the first-order system as the transfer function for a heat exchanger, more accurate models are built to derive the parameters K, T and respectively, which are constructed with a lumped parameter approach. Unlike a number of recent analyses K is obtained by using arithmetic mean temperature difference, log mean temperature difference has been employed instead, which minimized the error; time constant T is obtained by deriving the time constant of baffle; delay time is estimated by flow rate. The result shows that this method to study the dynamic characteristics of heat exchanger is easier, more accurate.

Transient heat transfert in coflow heat exchanger

More than ever before, dynamic investigation techniques are becoming widely used in the control systems, parameter implementation and state estimators. Indeed, dynamical models describing the response of process systems that are subject to disturbances play a vital role in controlling and optimising these systems. Recently developed in literature, the method of step response analysis provides a promising means towards solving some of the problems associated with the characterisation of transient response of heat exchangers. In Abdelghani-Idrissi et al. (Int J Heat Mass Transfer 44:3721–3730, 2001), authors present analytical expressions of fluids temperatures response time of counter-current heat exchanger when hot fluid step change is applied in the internal tube. This paper describes the extension of this technique to a coflow heat exchanger for which the exact solution of its mathematical model is unavailable.

Two Functions Used in the Analysis of Crossflow Exchangers, Regenerators, and Related Equipment

Two families of functions, which will be designated as G{sub n}(x,y) and F{sub n}(x,y), find use in the analysis of crossflow heat exchangers, regenerators, packed beds, the transient response of heat exchangers, and related problems. Larsen gives four place tables for G{sub {minus}1}, G{sub 0}, G{sub 1}, F{sub 0}, and F{sub 1} (X,y) (x and y; 0, (1), 20). However, in many applications the values of the functions are required for larger values of the index n, larger values of x and y, and for both arguments negative. The dual purpose of this note is to summarize some properties of the functions and to indicate a rapid method of finding their numerical values.

Transient Response of Heat Exchangers with One Infinite Capacitance Fluid

Abstract Information on the transient response of heat exchangers is essential to produce the optimum heat exchanger operation for the required function. A transient response analysis is presented for a heat exchanger with an infinite capacitance fluid on the shell side. The inlet temperature of the finite capacity fluid is stepped, and the heat exchanger response is represented by the change in the temperature of this fluid at the outlet of the tubes. The results cover all practical combinations of the dependent parameters and are presented as a set of charts. Results of previous workers in this field are discussed. Their charts cover a very restricted range of heat transfer conditions and are therefore of limited use. In addition, assumptions have been incorporated into their analyses which result in major discrepancies.

The Transient Response of Heat Exchangers Having an Infinite Capacitance Rate Fluid

The transient response of heat exchangers to a step change in the temperature of the infinite capacitance rate fluid temperature is discussed. This work applies to condensers, evaporators, precoolers, and intercoolers. Analytical and finite difference methods are used to obtain solutions. The procedure for making useful hand calculations for the entire range of practical values of the parameters is presented.

The Transient Response of Gas-Turbine-Plant Heat Exchangers—Regenerators, Intercoolers, Precoolers, and Ducting

This is the second report of a program dealing with the transient response of heat exchangers [1a], [1b]. Analog solutions are used to supplement some analytical solutions so as to provide fairly complete coverage for the heat exchangers encountered in gas-turbine plants. Because a gas flow exists on at least one side of the heat-transfer surface, these exchangers are characterized by a large wall-capacitance effect. Where greater generality is possible, the extension to other heat exchangers is indicated.