scholarly journals Mathematical modeling of a multi-stream brazed aluminum plate fin heat exchanger

2010 ◽  
Vol 14 (1) ◽  
pp. 103-114 ◽  
Author(s):  
Ahmed Kohil ◽  
Hassan Farag ◽  
Mona Ossman
Keyword(s):  
Sensitivity Analysis ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Ethylene Plant ◽  
Inlet Flow Rate ◽  
Cold Stream ◽  
Inlet Conditions ◽  
Good Agreement

The need for small size and lightweight heat exchangers in many applications has resulted in the development of many heat transfer surfaces. This type of heat exchanger is much more compact than can be practically realized with circular tubes. In this work a steady-state mathematical model that representing one of the plate fin heat exchangers enclosed in cold box of an ethylene plant has been developed. This model could evaluate the performance of the heat exchanger by predicting the outlet temperatures of the hot and cold streams when the inlet conditions are known. The model has been validated by comparing the results with actual operating values and the results showed good agreement with the actual data. Sensitivity analysis was applied on the model to illustrate the main parameters that have the greatest influence on the model calculated results. The sensitivity analysis showed that the hot stream outlet temperature is more sensitive to cold streams inlet temperatures and less sensitive to hot stream inlet temperature and thermal resistance (fouling), while the cold stream outlet temperature is more sensitive to cold streams inlet flow rate and less sensitive to fouling.

scholarly journals Analytical and Experimental Investigation of a Plate Fin Heat Exchanger at Cryogenics Temperature

2021 ◽  
Vol 39 (4) ◽  
pp. 1225-1235
Author(s):  
Ajay K. Gupta ◽  
Manoj Kumar ◽  
Ranjit K. Sahoo ◽  
Sunil K. Sarangi
Keyword(s):  
Heat Exchanger ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Cryogenic Temperature ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Compact Size

Plate-fin heat exchangers provide a broad range of applications in many cryogenic industries for liquefaction and separation of gasses because of their excellent technical advantages such as high effectiveness, compact size, etc. Correlations are available for the design of a plate-fin heat exchanger, but experimental investigations are few at cryogenic temperature. In the present study, a cryogenic heat exchanger test setup has been designed and fabricated to investigate the performance of plate-fin heat exchanger at cryogenic temperature. Major parameters (Colburn factor, Friction factor, etc.) that affect the performance of plate-fin heat exchangers are provided concisely. The effect of mass flow rate and inlet temperature on the effectiveness and pressure drop of the heat exchanger are investigated. It is observed that with an increase in mass flow rate effectiveness and pressure drop increases. The present setup emphasis the systematic procedure to perform the experiment based on cryogenic operating conditions and represent its uncertainties level.

IMPORTANCE OF 3D VEHICLE HEAT EXCHANGER MODELING

2021 ◽  
pp. 1-10
Author(s):  
Michal Schmid ◽  
Fatih Bozkurt ◽  
Petr Pašcenko ◽  
Pavel Petržela
Keyword(s):  
Fluid Flow ◽  
Heat Exchanger ◽  
Fluid Velocity ◽  
Coolant Temperature ◽  
Inlet Temperature ◽  
Vehicle Simulation ◽  
Velocity Magnitude ◽  
Primary Fluid ◽  
The Difference ◽  
Inlet Conditions

Abstract The work demonstrates, via a comprehensive study, the necessity of using a 3D CFD approach for heat exchanger (HTX) modelling within underhood vehicle simulation. The results are presented as the difference between 1D and 3D CFD approaches with a focus on auxiliary fluid (e.g. coolant) temperature prediction as a function of primary fluid (e.g. air) inlet conditions. It has been shown that the 1D approach could significantly underpredict auxiliary fluid inlet temperature due to neglecting the spatial distribution of primary fluid velocity magnitude. The resultant difference in the auxiliary fluid flow HTX inlet temperature is presented and discussed as a function of the Uniformity Index (UI) of the primary fluid flow velocity magnitude. Additionally, the 3D HTX model's importance is demonstrated in an industrial example of full 3D underhood simulation.

Thermal Analysis Technique for Coolers Operating in Off and Low Load Conditions

2012 ◽  
Author(s):  
Thomas J. Muldoon
Keyword(s):  
Heat Exchanger ◽  
Power Plant ◽  
Heat Exchangers ◽  
Cooling Water ◽  
Control Valve ◽  
Operating Conditions ◽  
Outlet Temperature ◽  
Inlet Valve ◽  
Plant Personnel ◽  
Load Conditions

The most conservatively designed power plant heat exchangers are designed to meet a maximum heat load with minimum fluid temperature differences. When the input temperatures are less than design maximums, the cooler will usually be in a position of over performance. This relationship is especially true when the heat exchanger is a closed Component Cooling Water (CCW) heat exchanger with inlet fluid at ambient conditions. Maintaining a consistent cooling temperature is an important concern in the operation of a power plant. It is important that the cooling needs of the equipment such as the hydrogen coolers are maintained at a set temperature. Overcooling may not be of benefit to the equipment. The component which cools the service water with the local cooling water is a component cooling water heat exchanger (CCW). The two primary methods of controlling the heat rejection performance on these vessels is to throttling the tubeside flow to get a consistent shell outlet temperature with control valves or leave the tubeside flow constant and by-pass a portion of the shellside flow. Estimating the performance of the heat exchanger with given set of inlet conditions and a fixed design point can be accomplished using a the Number Transfer Units (NTU) method. Opening and closing the control valve is based on the estimated performance. This analysis can be used by power plant personnel to gauge the operation of these vessels over varying operating conditions. The analysis can also include the effect of different values of cleanliness and the extent of throttling. As a unit experiences fouling, additional flow is required to meet the thermal requirements. Depending upon the extent of fouling, the inlet valve will be either opened or closed. Plant personnel may observe the cooling water inlet temperature and the extent to which the inlet valve is open, and use that information to determine possible fouling and setup a maintenance schedule. The following analytical approach for evaluating low, critical, or off load conditions is important in the design and operation of these types of power plant heat exchangers, piping and control valve systems.

Response of a Single/Two-Pass, Liquid-Liquid heat Exchanger to Disturbances in Flow Rate

1967 ◽  
Vol 9 (3) ◽  
pp. 211-217
Author(s):  
I. C. Finlay ◽  
J. Smith
Keyword(s):  
Heat Exchanger ◽  
Flow Rate ◽  
Transfer Functions ◽  
Outlet Temperature ◽  
Lumped Model ◽  
Thermal Capacitance ◽  
Shell And Tube ◽  
Liquid Heat ◽  
Temperature Responses ◽  
Good Agreement

Transfer functions, relating outlet temperature responses to disturbances in flow rate, are presented for a single/two-pass heat exchanger with distributed wall and fluid thermal capacitance. Good agreement is shown between the measured and predicted outlet temperature responses of both shell and tube-side fluids. The accuracy of an overall lumped model as an approximation to such a system is examined.

scholarly journals Experimental determination of correlations for mean heat transfer coefficients in plate fin and tube heat exchangers

2012 ◽  
Vol 33 (3) ◽  
pp. 1-24 ◽  
Author(s):  
Dawid Taler
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Correlation Coefficients ◽  
Outlet Temperature ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nonlinear Regression Method ◽  
Propagation Rule

Abstract This paper presents a numerical method for determining heat transfer coefficients in cross-flow heat exchangers with extended heat exchange surfaces. Coefficients in the correlations defining heat transfer on the liquid- and air-side were determined using a nonlinear regression method. Correlation coefficients were determined from the condition that the sum of squared liquid and air temperature differences at the heat exchanger outlet, obtained by measurements and those calculated, achieved minimum. Minimum of the sum of the squares was found using the Levenberg-Marquardt method. The uncertainty in estimated parameters was determined using the error propagation rule by Gauss. The outlet temperature of the liquid and air leaving the heat exchanger was calculated using the analytical model of the heat exchanger.

Turbulent flows in a spiral double-pipe heat exchanger

2019 ◽  
Vol 30 (1) ◽  
pp. 39-53 ◽  
Author(s):  
Zhe Tian ◽  
Ali Abdollahi ◽  
Mahmoud Shariati ◽  
Atefeh Amindoust ◽  
Hossein Arasteh ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Turbulent Flows ◽  
Heat Exchangers ◽  
Volume Fraction ◽  
Inlet Temperature ◽  
Content Type ◽  
Tube Heat Exchanger ◽  
Double Pipe ◽  
Pipe Heat

Purpose This paper aims to study the fluid flow and heat transfer through a spiral double-pipe heat exchanger. Nowadays using spiral double-pipe heat exchangers has become popular in different industrial segments due to its complex and spiral structure, which causes an enhancement in heat transfer. Design/methodology/approach In these heat exchangers, by converting the fluid motion to the secondary motion, the heat transfer coefficient is greater than that of the straight double-pipe heat exchangers and cause increased heat transfer between fluids. Findings The present study, by using the Fluent software and nanofluid heat transfer simulation in a spiral double-tube heat exchanger, investigates the effects of operating parameters including fluid inlet velocity, volume fraction of nanoparticles, type of nanoparticles and fluid inlet temperature on heat transfer efficiency. Originality/value After presenting the results derived from the fluid numerical simulation and finding the optimal performance conditions using a genetic algorithm, it was found that water–Al2O3 and water–SiO2 nanofluids are the best choices for the Reynolds numbers ranging from 10,551 to 17,220 and 17,220 to 31,910, respectively.

scholarly journals Evaluation of a counter-flow microchannel heat exchanger performance with air-water vapor mixture to liquid water

2020 ◽  
Vol 194 ◽  
pp. 01025
Author(s):  
C. Ren ◽  
J.H. Weng ◽  
J.N. Yan ◽  
L. Wang ◽  
H.L. She ◽  
...  
Keyword(s):  
Water Vapor ◽  
Heat Exchanger ◽  
Liquid Water ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Vapor Mixture ◽  
Counter Flow ◽  
Microchannel Heat Exchanger ◽  
Operation Conditions ◽  
Continuum Flow

Given its configuration and operation conditions, the performance of a counter-flow microchannel heat exchanger (MCHX) is evaluated through detailed calculations. The fluids, both liquid water and air, are considered as continuum flow flowing in microchannels. The MCHX has 59 sheets, and each sheet has 48 microchannels. The microchannels for both fluids have the same cross section of 0.8mm×1mm and same length of 200mm. Log mean temperature difference method is adopted for this evaluation. Using appropriate equations, the properties of air-water vapor mixture are calculated based on that of the two components. Given the inlet temperature for liquid water(35℃) and air (170℃),the calculated outlet temperature for both fluids are 55.5℃ and 43.3℃, respectively. The results also show that the air at the outlet is saturated. The overall heat transfer coefficient reaches 100W/m2ꞏK, which is much higher than that of conventional heat exchanger with similar fluid combinations.

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.

Second-Law-Based Thermoeconomic Optimization of Two-Phase Heat Exchangers

1987 ◽  
Vol 109 (2) ◽  
pp. 287-294 ◽  
Author(s):  
S. M. Zubair ◽  
P. V. Kadaba ◽  
R. B. Evans
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Unit Cost ◽  
Second Law ◽  
Inlet Temperature ◽  
Two Phase ◽  
Transfer Resistance

This paper presents a closed-form analytical method for the second-law-based thermoeconomic optimization of two-phase heat exchangers used as condensers or evaporators. The concept of “internal economy” as a means of estimating the economic value of entropy generated (due to finite temperature difference heat transfer and pressure drops) has been proposed, thus permitting the engineer to trade the cost of entropy generation in the heat exchanger against its capital expenditure. Results are presented in terms of the optimum heat exchanger area as a function of the exit/inlet temperature ratio of the coolant, unit cost of energy dissipated, and the optimum overall heat transfer coefficient. The total heat transfer resistance represented by (1/U = C1 + C2 Re−n) in the present analysis is patterned after Wilson (1915) which accommodates the complexities associated with the determination of the two-phase heat transfer coefficient and the buildup of surface scaling resistances. The analysis of a water-cooled condenser and an air-cooled evaporator is presented with supporting numerical examples which are based on the thermoeconomic optimization procedure of this paper.

Sensitivity Analysis for Shell-and-Tube Heat Exchangers Based on Entropy Production

2012 ◽  
Vol 516-517 ◽  
pp. 419-424
Author(s):  
Guo Rong Zhu ◽  
Xiao Hua Wang ◽  
Hong Biao Huang ◽  
Hu Chen
Keyword(s):  
Heat Transfer ◽  
Sensitivity Analysis ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Entropy Production ◽  
Heat Exchangers ◽  
Structural Parameters ◽  
Flow Process ◽  
Tube Heat Exchanger ◽  
Shell And Tube

In this article, sensitivity analysis was performed using bidirectional single method with shell-and-tube heat exchanger as the basis and the entropy production in the working process of heat exchanger as target, to explore the optimizing direction for heat exchangers with the objective to reduce entropy production. First, the differential element analysis method was used in a case study of the entropy production of the heat transfer process - including the three heat transfer processes of convective heat exchange inside and outside the pipes and heat conduction across the pipe wall and the flow process - the fluid flowing process inside and outside the pipes, and the typical process parameter - dimensionless inlet heat exchange temperature difference, operation parameter - fluid flow rate inside the pipe and structural parameters - the heat transfer pipe inner diameter and length were used as characteristic parameters, to obtain the sensitivity coefficients under the conditions of the example, being respectively 0.95, 0.3, 0.3 and 0.38. The study in this article can provide some support to the energy efficiency evaluation of heat exchangers.

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