scholarly journals Heat exchanger operating point determination

2009 ◽  
Vol 13 (4) ◽  
pp. 151-164
Author(s):  
Dusan Gvozdenac
Keyword(s):  
Mathematical Model ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Operating Point ◽  
Operating Parameters ◽  
Heat Flow Rate ◽  
Point Determination ◽  
Operating Points ◽  
Special Case ◽  
Micro Balance

This paper indicates 21 possible tasks for the calculation of heat exchangers and specifies in particular the procedure for determining heat exchanger operating point. Features of heat exchanger energy micro-balance are contained in its mathematical model, and features of its macro-balance hold in relations for heat flow rate. Operating point of heat exchanger is defined by satisfying micro and macro balances. The paper presents basic relations for determining operating points for some types of tasks and algorithms of certain procedures. A special case in which two, one or none non-trivial solutions appear within two of 21 tasks is analyzed and discussed separately. Presented procedures are very suitable for the preparation of own software for the calculation of operating parameters of any heat exchanger and analysis of heat exchangers network.

scholarly journals Experimental Verification of an Analytical Mathematical Model of a Round or Oval Tube Two-Row Car Radiator

Energies ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3399
Author(s):  
Dawid Taler ◽  
Jan Taler ◽  
Marcin Trojan
Keyword(s):  
Mathematical Model ◽  
Heat Exchanger ◽  
Heat Flow ◽  
Heat Exchangers ◽  
Cfd Simulation ◽  
Experimental Studies ◽  
Hot Water ◽  
Heat Flow Rate ◽  
Cfd Modelling ◽  
Tube Heat Exchanger

The paper presents an analytical mathematical model of a car radiator, which takes into account various heat transfer coefficients (HTCs) on each row of pipes. The air-side HTCs in a specific row of pipes in the first and second passes were calculated using equations for the Nusselt number, which were determined by CFD simulation by the ANSYS program (Version 19.1, Ansys Inc., Canonsburg, PA, USA). The liquid flow in the pipes can be laminar, transition, or turbulent. When changing the flow form from laminar to transition and from transition to turbulent, the HTC continuity is maintained. Mathematical models of two radiators were developed, one of which was made of round tubes and the other of oval tubes. The model allows for the calculation of the thermal output of every row of pipes in both passes of the heat exchangers. Small relative differences between the total heat flow transferred in the heat exchanger from hot water to cool air exist for different and uniform HTCs. However, the heat flow rate in the first row is much higher than the heat flow in the second row if the air-side HTCs are different for each row compared to a situation where the HTC is constant throughout the heat exchanger. The thermal capacities of both radiators calculated using the developed mathematical model were compared with the results of experimental studies. The plate-fin and tube heat exchanger (PFTHE) modeling procedure developed in the article does not require the use of empirical correlations to calculate HTCs on both sides of the pipes. The suggested method of calculating plate-fin and tube heat exchangers, taking into account the different air-side HTCs estimated using CFD modelling, may significantly reduce the cost of experimental research for a new design of heat exchangers implemented in manufacturing.

scholarly journals RESEARCH OF THE DIRECTIONS OF IMPROVEMENT OF PLATE EXCHANGER HEAT EXCHANGERS

2019 ◽  
pp. 59-65
Author(s):  
Iryna Gunko ◽  
Ivan Sevostyanov ◽  
Yuriy Orlyuk
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Dairy Products ◽  
High Reliability ◽  
Construction Cost ◽  
Plate Heat Exchanger ◽  
Operating Parameters ◽  
Maintenance And Repair ◽  
Plate Heat ◽  
Advantages And Disadvantages

The article provides an analysis of the known schemes of plate heat exchangers, their advantages and disadvantages, as well as areas for improvement. Taking into account the results of the analysis conducted in the department of dairy products of the Institute of Food Resources of the National Academy of Agrarian Sciences of Ukraine, the All-Ukrainian Scientific Research Educational Consortium, the authors developed an improved plate heat exchanger scheme, which combines high reliability, energy efficiency and heating rate of the coolant with simplicity, compactness and low construction cost, with ease of maintenance and repair (easy disassembly and cleaning). The dependences for the calculation of the main design and operating parameters of an improved heat exchanger are given.

scholarly journals Energy analysis of heat exchanger in a heat exchanger network

2018 ◽  
Vol 22 (5) ◽  
pp. 1999-2011 ◽  
Author(s):  
Martina Rauch ◽  
Antun Galovic
Keyword(s):  
Mathematical Model ◽  
Heat Exchanger ◽  
Heat Flow ◽  
Flow Rate ◽  
Local Extremum ◽  
Heat Flow Rate ◽  
Fluid Stream ◽  
Heat Exchanger Network ◽  
Maximum Heat ◽  
The Given

For many years now, heat exchanger optimization has been a field of research for a lot of scientists. Aims of optimization are different, having in mind heat exchanger networks with different temperatures of certain streams. In this paper mathematical model in dimensionless form is developed, describing operation of one heat exchanger in a heat exchanger network, with given overall area, based on the maximum heat-flow rate criterion. Under the presumption of heat exchanger being a part of the heat exchanger network, solution for the given task is resting in a possibility of connecting an additional fluid stream with certain temperature on a certain point of observed heat exchanger area. The connection point of additional fluid stream determines the exchanging areas of both heat exchangers and it needs to allow the maximum exchanged heat-flow rate. This needed heat-flow rate achieves higher value than the heat-flow rate acquired by either of streams. In other words, a criterion for the existence of the maximum heat-flow rate, as a local extremum, is obtained within this mathematical model. Results of the research are presented by the adequate diagrams and are interpreted, with emphasis on the cases which fulfill and those which do not fulfill the given condition for achieving the maximum heat-flow rate.

scholarly journals IDENTIFICATION OF MATHEMATICAL MODEL OF WATER LINE IN HEAT EXCHANGERS

2020 ◽  
pp. 34619-34622
Keyword(s):  
Mathematical Model ◽  
Heat Exchanger ◽  
Data Collection ◽  
Heat Exchangers ◽  
Computational Simulation ◽  
Suitable Model ◽  
Monitoring And Control ◽  
Computational Tool ◽  
Water Line ◽  
And Control

Heat exchangers are widely used in industries for the use of thermal energy generated from different processes. For a definite use of this energy, the temperatures of the hot and cold fluids passing through the heat exchanger must be monitored and controlled efficiently. A suitable model of the heat exchanger is required for monitoring and control purposes. The objective of this work is to mathematically model a heat exchanger using a system identification method using a computational tool. The methodology used consists of data collection and simulation of models, as well as the analysis of comparison of the estimated models with the real system. The results show that the identification through computational simulation presented satisfactory results.

scholarly journals Analysis of Three-Fluid, Crossflow Heat Exchangers

1968 ◽  
Vol 90 (3) ◽  
pp. 333-338 ◽  
Author(s):  
N. C. Willis ◽  
A. J. Chapman
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Operating Parameters ◽  
Inlet Temperature ◽  
Countercurrent Flow ◽  
Operating Variables ◽  
Effectiveness Factors ◽  
Wide Range ◽  
Temperature Parameter

In this study, the performance of three-fluid, crossflow heat exchangers is determined and presented graphically in terms of the temperature effectiveness of two of the fluids. The effectiveness is determined as a function of heat exchanger size for sets of fixed operating conditions. The introduction of nondimensional operating variables reduces the volume of data required to represent a practical range of operating conditions. The number of boundary conditions for the temperatures is reduced from three to one by the introduction of a nondimensional inlet temperature parameter. Effectiveness factors are determined for a wide range of operating parameters for single-pass, three-fluid heat exchangers. Performance of multipass three-fluid heat exchangers for both cocurrent and countercurrent flow is studied for selected operating conditions.

Reliability-Based Maintenance Strategies for Heat Exchangers Subject to Fouling

1996 ◽  
Vol 118 (4) ◽  
pp. 306-312 ◽  
Author(s):  
A. K. Sheikh ◽  
S. M. Zubair ◽  
M. U. Haq ◽  
M. O. Budair
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Unit Cost ◽  
Heat Transfer Process ◽  
Economic Behavior ◽  
Periodic Maintenance ◽  
Cleaning Cycle ◽  
Cost Parameters ◽  
Special Case ◽  
Additional Fuel

Fouling in heat exchangers is an unavoidable by-product of the heat transfer process. The decision regarding periodic maintenance (cleaning) of the exchangers subject to fouling is generally based on thermal and economic behavior of the process. In this paper, a reliability-based maintenance strategy is discussed by incorporating the risk and scatter parameters of the linear random fouling growth model. In addition, the dimensionless cost-objective function is formulated by considering various cost elements for a heat exchanger used in a crude oil preheat train. The variation in the dimensionless cost Γ with reduced time tp/(tp + tdown) is presented for different values of unit cost parameters γ1, γ2, and γ3 representing additional fuel cost, antifoulant cost, and miscellaneous costs, respectively. Furthermore, the optimal cleaning cycle of the heat exchanger recently investigated by Casado (1990) is demonstrated to be a special case of the results presented in the paper.

Experimental investigation and mathematical model of a heat exchanger with porous metal inserts

2020 ◽  
Vol 6 (2) ◽  
pp. 22-40
Author(s):  
Boris G. Aksenov ◽  
Oleg A. Stepanov ◽  
Natalia V. Rydalina
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Theoretical Data ◽  
Porous Metal ◽  
Porous Metals ◽  
Standard Methods ◽  
Porous Aluminum ◽  
The Status

When creating and manufacturing heat exchangers, one of the main tasks is to increase the efficiency of heat transfer. The use of porous metals in heat exchangers is one of the promising ways to increase the heat transfer intensity, which determines the relevance of the study. The paper provides an overview of the status of this issue on literary sources. The purpose of the work is to conduct an experimental study of a heat exchanger with porous materials, to compile a mathematical model that allows analytical calculations of such heat exchangers, to confirm the correctness of the compiled model experimentally. An experimental bench has been created to study a heat exchanger that uses porous aluminum. The hot fluid is warm water that flows through pipes passing through a porous metal. The cold coolant flowing through the pores is freon, which cools the water. A schematic diagram and description of the stand are presented. A test cycle has been conducted. A comparison of the heat transfer intensity for materials of different porosity is given. Using standard methods for calculating heat exchangers in this case is not possible due to the lack of standard methods for determining the area of the inner surface with pores. In the course of the work, the standard equation describing the cooling of a porous body was proposed to be supplemented by the function of distributed heat sources. As a result, we have obtained a mathematical model of the heat exchanger under consideration in a simplified form, which can be used in technical calculations. The calculation results by the obtained method are correlated with the data of experiments. Deviations of empirical and theoretical data are within acceptable limits. The results obtained make it possible to use porous metals in order to increase the heat transfer intensity in the manufacture of heat exchangers. This technique allows calculations with an unknown heat exchange surface area, taking into account the heat capacity and heat of phase transition, if any. According to the methodology, the article is experimental-theoretical. Experiments are being conducted on the created laboratory bench. In parallel, calculations are made according to the developed mathematical model. The results are compared. Conclusions are made of a theoretical and applied nature.

scholarly journals Calculation of the Efficiency of Regenerative Air Heat Exchanger with Intermediate Heat Carrier

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Mikhail Ivanovich Nizovtsev ◽  
V. Yu. Borodulin
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Heat Exchanger ◽  
Heat Carrier ◽  
Heat Transfer Process ◽  
Maximum Temperature ◽  
Operating Parameters ◽  
Air Flow Rate ◽  
Filling Height ◽  
Temperature Efficiency

The study deals with a new regenerative air heat exchanger with an intermediate heat carrier used in the systems of room ventilation. A physical and mathematical model of the heat transfer process is proposed. The influence of design and operating parameters on the temperature efficiency of the heat exchanger is analyzed. The possibility of a significant increase in its efficiency with a decrease in the packing diameter is shown. As a result of calculations, it was found that with a decrease in the filling height, the maximum temperature efficiency shifted towards a decrease in the air flow rate from its value determined from the equality of water equivalents of liquid and air.

scholarly journals Application of porous materials in heat exchangers of heat supply system

2020 ◽  
Vol 22 (3) ◽  
pp. 3-13
Author(s):  
N. V. Rydalina ◽  
B. G. Aksenov ◽  
O. A. Stepanov ◽  
E. O. Antonova
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mathematical Model ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Porous Materials ◽  
Heat Exchangers ◽  
Porous Metals ◽  
Porous Aluminum ◽  
Heat Exchange Equipment

Heat exchange capacity increase is one of the main concerns in the process of manufacturing modern heat exchange equipment. Constructing heat exchangers with porous metals is an advanced technique of heat exchange increase. A construction of heat exchangers with porous aluminum is described in this paper. The first heat transfer agent (hot water) flows through thin copper tubes installed within the porous aluminum. The second heat transfer agent (freon) flows through the pores of aluminum. Laboratory facility was created to study such a heat exchanger. Series of experiments were carried out. The purpose of the research presented here is to create a mathematical model of heat exchangers with porous metals, to perform analytical calculation of the heat exchangers and to confirm the results with the experimental data. In this case, one can`t use the standard methods of heat exchangers calculation because the pores inner surface area is indeterminate. The developed mathematical model is based on the equation describing the process of cooling the porous plate. A special mathematical technique is used to take into account the effect of tubes with water. The model is approximate but its solution is analytic. It is convenient. One can differentiate it or integrate it, which is very important. Comparison of calculated and experimental data is performed. Divergence of results is within the limits of experimental error. If freon volatilizes inside the heat exchanger, the heat of phase transition has to be taken into account alongside with heat capacity. The structure of the mathematical model makes it possible. The results presented in this paper prove the practicability of using porous materials in heat exchange equipment.

scholarly journals Mathematical model of a plate fin heat exchanger operating under solid oxide fuel cell working conditions

2013 ◽  
Vol 34 (4) ◽  
pp. 3-21 ◽  
Author(s):  
Jakub Kupecki ◽  
Krzysztof Badyda
Keyword(s):  
Mathematical Model ◽  
Fuel Cells ◽  
Heat Exchanger ◽  
Power Systems ◽  
Solid Oxide Fuel Cells ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Solid Oxide ◽  
System Level ◽  
Oxide Fuel

Abstract Heat exchangers of different types find application in power systems based on solid oxide fuel cells (SOFC). Compact plate fin heat exchangers are typically found to perfectly fit systems with power output under 5 kWel. Micro-combined heat and power (micro-CHP) units with solid oxide fuel cells can exhibit high electrical and overall efficiencies, exceeding 85%, respectively. These values can be achieved only when high thermal integration of a system is assured. Selection and sizing of heat exchangers play a crucial role and should be done with caution. Moreover, performance of heat exchangers under variable operating conditions can strongly influence efficiency of the complete system. For that reason, it becomes important to develop high fidelity mathematical models allowing evaluation of heat exchangers under modified operating conditions, in high temperature regimes. Prediction of pressure and temperatures drops at the exit of cold and hot sides are important for system-level studies. Paper presents dedicated mathematical model used for evaluation of a plate fin heat exchanger, operating as a part of micro-CHP unit with solid oxide fuel cells.

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