Computer Aided Optimal Design of Heat Exchanger Networks

1991 ◽  
Author(s):  
P. Seshadri ◽  
Larry C. Witte
Keyword(s):  
Heat Exchanger ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Minimum Temperature ◽  
Mathematical Formulation ◽  
Computer Algorithms ◽  
Pinch Point ◽  
Pinch Technology ◽  
Computer Based ◽  
Economic Considerations

Abstract A method for finding the best (optimal) operating layout of heat exchangers in complicated thermal networks is developed in this paper. Computer algorithms are developed that take advantage of pinch technology and economic considerations, and exergetic constraints as well as conventional heat and mass balances. Our goals were to achieve minimum loss of exergy between hot and cold streams subject to practical system constraints. Furthermore, resulting networks should be limited to no more units than the theoretical minimum. The ultimate goal was to minimize investment and operating costs for a set of fixed overall system constaints. These goals were realized by developing a computer-based nonlinear multiple objective optimization algorithm that included the elements discussed above. The final solution is a synthesis of the best system using the above-described mathematical formulation. Results for a 4-stream heat exchanger network are presented in terms of the minimum temperature difference at the pinch point. The influence of the minimum temperature difference on capital cost, heat transfer area, exergetic losses and second law efficiency of various heat exchangers in the network is presented.

Analysis of the Thermal Stress at the Tubesheet in Floating-Head or U-Tube Heat Exchangers

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Jiuyi Liu ◽  
Caifu Qian ◽  
Huifang Li
Keyword(s):  
Thermal Stress ◽  
Heat Exchanger ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Influence Factors ◽  
Area Ratio ◽  
Shell Side ◽  
Tube Heat Exchanger ◽  
Numerical Tests ◽  
Hole Area

Thermal stress is an important factor influencing the strength of a heat exchanger tubesheet. Some studies have indicated that, even in floating-head or U-tube heat exchangers, the thermal stress at the tubesheet is significant in magnitude. For exploring the value, distribution, and the influence factors of the thermal stress at the tubesheet of these kind heat exchangers, a tubesheet and triangle arranged tubes with the tube diameter of 25 mm were numerically analyzed. Specifically, the thermal stress at the tubesheet center is concentrated and analyzed with changing different parameters of the tubesheet, such as the temperature difference between tube-side and shell-side fluids, tubesheet diameter, thickness, and the tube-hole area ratio. It is found that the thermal stress of the tubesheet of floating-head or U-tube heat exchanger was comparable in magnitude with that produced by pressures, and the distribution of the thermal stress depends on the tube-hole area and the temperature inside the tubes. The thermal stress at the center of the tubesheet surface is high when tube-hole area ratio is very low. And with increasing the tube-hole area ratio, the stress first decreases rapidly and then increases linearly. A formula was numerically fitted for calculating the thermal stress at the tubesheet surface center which may be useful for the strength design of the tubesheet of floating-head or U-tube heat exchangers when considering the thermal stress. Numerical tests show that the fitted formula can meet the accuracy requirements for engineering applications.

scholarly journals Study of the Performance of a Novel Radiator with Three Inlets and One Outlet Based on Topology Optimization

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 594
Author(s):  
Tao Zhou ◽  
Bingchao Chen ◽  
Huanling Liu
Keyword(s):  
Topology Optimization ◽  
Heat Exchanger ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Exchange Capacity ◽  
Numerical Results ◽  
Fluid Temperature ◽  
Channel Depth ◽  
Goal Model ◽  
Flow And Heat Transfer

In recent years, in order to obtain a radiator with strong heat exchange capacity, researchers have proposed a lot of heat exchangers to improve heat exchange capacity significantly. However, the cooling abilities of heat exchangers designed by traditional design methods is limited even if the geometric parameters are optimized at the same time. However, using topology optimization to design heat exchangers can overcome this design limitation. Furthermore, researchers have used topology optimization theory to designed one-to-one and many-to-many inlet and outlet heat exchangers because it can effectively increase the heat dissipation rate. In particular, it can further decrease the hot-spot temperature for many-to-many inlet and outlet heat exchangers. Therefore, this article proposes novel heat exchangers with three inlets and one outlet designed by topology optimization to decrease the fluid temperature at the outlet. Subsequently, the effect of the channel depth on the heat exchanger design is also studied. The results show that the type of exchanger varies with the channel depth, and there exists a critical depth value for obtaining the minimum substrate temperature difference. Then, the flow and heat transfer performance of the heat exchangers are numerically investigated. The numerical results show that the heat exchanger derived by topology optimization with the minimum temperature difference as the goal (Model-2) is the best design for flow and heat transfer performance compared to other heat sink designs, including the heat exchanger derived by topology optimization having the average temperature as the goal (Model-1) and conventional straight channels (Model-3). The temperature difference of Model-1 can be reduced by 37.5%, and that of Model-2 can be decreased by 62.5% compared to Model-3. Compared with Model-3, the thermal resistance of Model-1 can be reduced by 21.86%, while that of Model-2 can be decreased by 47.99%. At room temperature, we carried out the forced convention experimental test for Model-2 to measure its physical parameters (temperature, pressure drop) to verify the numerical results. The error of the average wall temperature between experimental results and simulation results is within 2.6 K, while that of the fluid temperature between the experimental and simulation results is within 1.4 K, and the maximum deviation of the measured Nu and simulated Nu was less than 5%. This indicated that the numerical results agreed well with the experimental results.

scholarly journals Energy and economy savings in the process of methanol synthesis unsig Pinch technology

2004 ◽  
Vol 69 (10) ◽  
pp. 827-837 ◽  
Author(s):  
Mirjana Kijevcanin ◽  
Bojan Djordjevic ◽  
Ozren Ocic ◽  
Mladen Crnomarkovic ◽  
Maja Maric ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Methanol Synthesis ◽  
Heat Exchangers ◽  
Energy Savings ◽  
Energy Costs ◽  
Pinch Analysis ◽  
Trade Off ◽  
Total Cost ◽  
Capital Costs ◽  
Pinch Technology

A heat exchanger network (HEN) for the process of methanol synthesis has been studied by pinch design analysis. Great economic and energy savings were realized by the pinch analysis in comparison to the existing plant. Also, it was found that it is possible to reduce the requirements for the consumption of utilities. The HEN was reconstruded by adding new heat exchangers. In order to produce new HEN, the capital costs had to be increased, but the total cost trade-off between the capital and energy costs will be decrease by 30 %.

Arithmetic Mean Temperature Difference and the Concept of Heat Exchanger Efficiency

2003 ◽  
Author(s):  
Ahmad Fakheri
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Arithmetic Mean ◽  
Counter Flow ◽  
Mean Temperature ◽  
Optimum Heat

In this paper, it is shown that the Arithmetic Mean Temperature Difference, which is the difference between the average temperatures of hot and cold fluids, can be used instead of the Log Mean Temperature Difference (LMTD) in heat exchanger analysis. For a given value of AMTD, there exists an optimum heat transfer rate, Qopt, given by the product of UA and AMTD such that the rate of heat transfer in the heat exchanger is always less than this optimum value. The optimum heat transfer rate takes place in a balanced counter flow heat exchanger and by using this optimum rate of heat transfer, the concept of heat exchanger efficiency is introduced as the ratio of the actual to optimum heat transfer rate. A general algebraic expression as well as a chart is presented for the determination of the efficiency and therefore the rate of heat transfer for parallel flow, counter flow, single stream, as well as shell and tube heat exchangers with any number of shells and even number of tube passes per shell. In addition to being more intuitive, the use of AMTD and the heat exchanger efficiency allow the direct comparison of the different types of heat exchangers.

Two Principles of Differential Second Law Heat Exchanger Design

1991 ◽  
Vol 113 (2) ◽  
pp. 329-336 ◽  
Author(s):  
R. B. Evans ◽  
M. R. von Spakovsky
Keyword(s):  
Heat Exchanger ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Second Law ◽  
First Principle ◽  
Heat Exchanger Design ◽  
Geometric Average ◽  
Mean Temperature ◽  
Second Law Analysis ◽  
Basic Treatment

In this paper, two fundamental principles of differential Second Law analysis are set forth for heat exchanger design. The first principle defines a Second Law temperature, while the second principle defines a Second Law temperature difference. The square of the ratio of the Second Law temperature difference to the Second Law temperature is shown always to be equal to the negative of the partial derivative of the rate of entropy generation (for heat transfer) with respect to the overall conductance of the heat exchanger. For the basic design of elementary heat exchangers, each of these two Second Law quantities is shown to take the form of a simple geometric average. Nonelementary considerations result in corrected geometric averages, which relate directly to the corrected log-mean temperature difference. Both the corrected log-mean temperature difference (nonelementary considerations) and the uncorrected or just log-mean temperature difference (elementary considerations) are widely used in heat exchanger analysis. The importance of these two principles in both exergy and essergy analysis is illustrated by a unified basic treatment of the optimum design of elementary heat exchangers. This results in a single optimization expression for all flow arrangements (i.e., counterflow, parallel flow, and certain crossflow cases).

Theoretical Analysis of Effects of Solution Heat Exchanger on the Performance of Mixed Absorption Refrigeration Cycle

2012 ◽  
Vol 170-173 ◽  
pp. 2521-2524
Author(s):  
Wen Li ◽  
Jun Hua Wan ◽  
Jing Liu ◽  
Zu Yi Zheng ◽  
Wen Ming Xu
Keyword(s):  
Heat Exchanger ◽  
Theoretical Analysis ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Water Flow Rate ◽  
Cooling Water ◽  
Solution Temperature ◽  
Refrigeration Cycle ◽  
Absorption Refrigeration ◽  
Cooling Water Flow Rate

The model of solution heat exchangers of mixed absorption refrigeration cycle was developed. The effects of strong solution temperature difference between inlet and outlet of solution heat exchanger on the coefficient of performance (COP) and cooling water flow rate of mixed absorption refrigeration cycle were analyzed, at the same time, the effects of temperature difference on the unit heat exchange area of counter-flow and cross-flow solution heat exchangers were analyzed. The theoretical analysis results showed that there was an optimal value for the strong solution temperature difference, for the mixed absorption system, the optimal temperature difference was about 12°C, the corresponding COP was 11.2% higher and the cooling water flow rate was 7.8% less than that of system without heat exchanger.

scholarly journals Heat Exchanger Process Optimization in A Typical Brewery Plant

2020 ◽  
Vol 5 (1) ◽  
pp. 76-81
Author(s):  
Shadrack Uzoma Mathew ◽  
Lebari Aban Tamzor
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Waste Heat ◽  
Production Capacity ◽  
Network System ◽  
Heat Exchanger Network ◽  
Heat System ◽  
Pinch Technology ◽  
Cold Stream ◽  
Gross Energy

The research attempts to improve upon the performance efficiency of the heat exchanger network system of Pabod Brewery, Port Harcourt, Rivers State, Nigeria. It swaps the heat system of the plant by the use of Pinch Technology to recover waste heat and integrating the recovered energy for process application. The application software is Microsoft Excel and Problem Table Method was employed in the numerical analysis of data. The gross energy expenditure by the plant is 10.44MW at production capacity of 400,000 liters of beer per day. On quantitative aggregate 6.157MW goes for heating and 4.267MW for cooling. A temperature pinch or minimum approach temperature (ΔTmin)of 100C was used in the pinch analysis of the heat exchangers performance. The research findings confirmed minimum heating utility of 5.04MW and cooling utility of 3.09MW. with energy upturn of 1.08MW and 1.23MW for the hot and cold flows respectively. This correlates to energy conservation of 18% for hot utility and 21% for the cold utility. The hot stream pinch temperature is 710C while that of the cold stream is 610C. Heat exchangers network configuration design were performed above and below the pinch The network designs were produced and integrated to produce improved heat exchanger network system for the Brewery plant.

scholarly journals HEAT EXCHANGER NETWORK SYNTHESIS CONSIDERING CHANGING PHASE STREAMS

2004 ◽  
Vol 3 (2) ◽  
Author(s):  
F. S. Liporace ◽  
F. L. P. Pessoa ◽  
E. M. Queiroz
Keyword(s):  
Heat Exchanger ◽  
Temperature Difference ◽  
Design Method ◽  
Enthalpy Change ◽  
Network Synthesis ◽  
Pinch Point ◽  
Specific Heats ◽  
Temperature Ranges ◽  
Heat Exchanger Network Synthesis

The Pinch Design Method was developed considering one-phase streams, with constant specific heats (Cp) throughout streams’ temperature ranges. Its first stage, the determination of utilities targets and pinch point (PP), is ruled by the number of streams, their temperatures and MCp. But, for changing phase streams, the usual description of the Cp behavior by a constant value can lead to errors in this stage and, hence, in the synthesis one. This work proposes a procedure to deal with these streams and discusses its results through an example involving multicomponent streams. First, bubble (BP) and dew (DP) points of the streams are estimated. Then, changing phase streams are split into sub-streams, using BP and DP as bounds. For each one, an effective Cp is estimated as the division of the enthalpy change by the respective temperature difference. Results obtained show significant changes on the PP, utilities targets and network proposed structure.

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