Transient response of a meso heat exchanger with temperature step variation

2018 ◽  
Vol 122 ◽  
pp. 1172-1181 ◽  
Author(s):  
Shahram Fotowat ◽  
Serena Askar ◽  
Amir Fartaj
Keyword(s):  
Heat Exchanger ◽  
Transient Response ◽  
Temperature Step

Numerical and Experimental Investigation of Transient Response of Primary Surface Recuperator Due to Flow Rate Step

2008 ◽  
Author(s):  
Zhenyu Liu ◽  
Yongkang Su ◽  
Huier Cheng
Keyword(s):  
Heat Exchanger ◽  
Transient Response ◽  
Flow Rate ◽  
Solid Wall ◽  
Structural Characteristics ◽  
Sudden Change ◽  
Transient Behavior ◽  
Temperature Transient ◽  
Rate Step ◽  
Comparative Results

Temperature transient response of a primary surface recuperator (PSR) is investigated when mass flow rate is subjected to a sudden change. Based on the conservation theorem of energy and structural characteristics of PSR, its unsteady differential equations about the transient temperatures of fluids and solid wall in the recuperator are presented. The numerical results are validated by comparison against the experimental data. The influence of flow rate step magnitude on the transient behavior is studied by maintaining the initial steady states. The influence of the thickness of the corrugated heat transfer foils in the PSR on the temperature transient response is also discussed. The comparative results show the low-weight PSR has much more advantages in transient response than traditional heat exchanger because its time constant of solid wall is much less than shell-tube or plate-fin heat exchanger. PSR is very fit for application to the marine or vehicle gas turbine engine that works under the changeful conditions.

Effect of Flow Maldistribution and Viscosity Variations on Transient Response of Plate Heat Exchangers: A Comparison With Uniform Flow and Constant Viscosity Model

Volume 1 ◽  
2004 ◽  
Author(s):  
H. Shokouhmand ◽  
N. Khareghani
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Transient Response ◽  
Heat Exchangers ◽  
Uniform Flow ◽  
Viscosity Model ◽  
Step Response ◽  
Plate Heat ◽  
Constant Viscosity ◽  
Flow Maldistribution

In this paper, transient response of plate heat exchangers under flow maldistribution and viscosity variations is discussed. This transient response is compared with the response achieved from uniform flow and constant viscosity through the exchanger. Flow maldistribution (unequal flow in channels) is calculated for U and Z types of plate heat exchangers. This flow maldistribution along with viscosity variations, during the growth of the temperature profile in each channel, affect the convective heat transfer coefficient in the transient period of heat transfer, and make it to be different from that of the other channels. These conditions make the transient response of a plate heat exchanger to have some deviations from the uniform flow and constant viscosity model response, which is discussed in this paper. The governing equations of heat transfer are solved using finite difference methods. Frequency response as well as step response of the heat exchanger is implemented as a time dependent initial conditions.

Transient response of a two layer cryogenic compact plate fin heat exchanger

2016 ◽  
Vol 41 (1) ◽  
pp. 45
Author(s):  
Abhilash Chakravarty ◽  
Mukesh Goyal ◽  
Anindya Chakravarty
Keyword(s):  
Heat Exchanger ◽  
Transient Response

Transient Response of Two-Phase Heat Exchanger With Varying Convection Coefficients

2006 ◽  
Vol 128 (9) ◽  
pp. 953-962 ◽  
Author(s):  
G. F. Naterer ◽  
C. H. Lam
Keyword(s):  
Heat Exchanger ◽  
Transient Response ◽  
Two Phase ◽  
Efficient Procedure ◽  
Integral Methods ◽  
Numerical Studies ◽  
Dynamic Simulator ◽  
Past Data ◽  
Energy Equations ◽  
Multiple Step

Transient changes of fluid and wall temperatures in a two-phase heat exchanger are investigated in this article, particularly with respect to spatial and temporal effects of varying convection coefficients. The coupled energy equations for both sides of the heat exchanger are solved directly with an integral method. Varying convection coefficients are related to changes of vapor fraction between the inlet and outlet of the heat exchanger. Unlike past numerical studies encountering difficulties with instability, stiffness, and lack of convergence, the current integral formulation provides a reliable alternative and efficient procedure for transient response within the heat exchanger. Furthermore, complex inversion from a transformed domain is not needed, in contrast to conventional methods with Laplace transforms. In this article, past integral methods are extended to cases with varying convection coefficients, arising from changes of phase fraction on the two-phase side of the heat exchanger, as well a multiple step-changes of temperature. The predicted results show close agreement with past data, including numerical simulations with a dynamic simulator.

Review and Analysis of Cross Flow Heat Exchanger Transient Modeling for Flow Rate and Temperature Variations

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Tianyi Gao ◽  
James Geer ◽  
Bahgat Sammakia
Keyword(s):  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Transient Response ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Inlet Temperature ◽  
Flow Rate Change ◽  
Flow Heat

Heat exchangers are important facilities that are widely used in heating, ventilating, and air conditioning (HVAC) systems. For example, heat exchangers are the primary units used in the design of the heat transfer loops of cooling systems for data centers. The performance of a heat exchanger strongly influences the thermal performance of the entire cooling system. The prediction of transient phenomenon of heat exchangers is of increasing interest in many application areas. In this work, a dynamic thermal model for a cross flow heat exchanger is solved numerically in order to predict the transient response under step changes in the fluid mass flow rate and the fluid inlet temperature. Transient responses of both the primary and secondary fluid outlet temperatures are characterized under different scenarios, including fluid mass flow rate change and a combination of changes in the fluid inlet temperature and the mass flow rate. In the ε-NTU (number of transfer units) method, the minimum capacity, denoted by Cmin, is the smaller of Ch and Cc. Due to a mass flow rate change, Cmin may vary from one fluid to another fluid. The numerical procedure and transient response regarding the case of varying Cmin are investigated in detail in this study. A review and comparison of several journal articles related to the similar topic are performed. Several sets of data available in the literatures which are in error are studied and analyzed in detail.

Numerical modeling transient response of tubular cross flow heat exchanger

2018 ◽  
Vol 28 (1) ◽  
pp. 81-91 ◽  
Author(s):  
Dawid Taler ◽  
Anna Korzen
Keyword(s):  
Nusselt Number ◽  
Heat Exchanger ◽  
Transient Response ◽  
Volume Flow ◽  
Water Volume ◽  
Transition Range ◽  
Content Type ◽  
Tube Heat Exchanger ◽  
Water Side ◽  
The Relationship

Purpose The paper aims to present the mathematical modeling of plate fin and tube heat exchanger at small Reynolds numbers on the water side. The Reynolds number of the water flowing inside the tubes was varied in the range from 4,000 to 12,000. Design/methodology/approach A detailed analysis of transient response was modeled for the following changes in the operating parameters of the heat exchanger: a reduction in the water volume flow, an increase in the water volume flow and an increase in the water volume flow with a simultaneous reduction in the air flow velocity. Findings The results of the numerical simulation of a heat exchanger by using experimentally determined water-side heat transfer correlation and theoretical correlation derived for the transition tube flow agree very well. The relationship to calculate the air-side Nusselt number was determined experimentally. The correlation for the air-side Nusselt number was the same for the theoretical and experimental water side correlation. Research limitations/implications The correlation for the air-side Nusselt number as a function of the Reynolds and Prandtl numbers is based on the experimental data and was determined using the least squares method. Originality/value The form of the relationship that was used to approximate experimentally determined water-side Nusselt numbers is identical to the theoretically derived formula for the transition range. The experiments show that the relationship for the water-side Nusselt number in transition and turbulent flow regime that was obtained using theoretical analysis gives quite satisfactory results.

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