scholarly journals Matrix method to solve inverse problem of heat transfer in heat exchangers with phase transition in heat carriers

Vestnik IGEU ◽  
2021 ◽  
pp. 68-75
Author(s):  
A.E. Barochkin
Keyword(s):  
Heat Transfer ◽  
Phase Transition ◽  
Inverse Problem ◽  
Heat Exchangers ◽  
Power Plants ◽  
Thermal Power ◽  
Energy Performance ◽  
Steam Boiler ◽  
Resource Saving ◽  
Heat Carriers

The transition to environmentally friendly and resource-saving energy, efficient use of natural resources and energy performance are the key priorities of the state energy policy of the Russian Federation. Maximum use of heat combustion of fuel and simultaneously production of condensate water of the combustion products of natural gas is one of the directions of energy saving policy. Despite many scientific papers on the issues of utilization of flue gas heat, condensation heat exchangers are not used in most gas boiler houses, energy power providers and thermal power plants in this country. And there are several reasons to explain this fact due to the lack of universal methods to calculate and design condensation-type heat exchangers. Thus, the development of new methods to simulate multithreaded heat exchangers considering the phase transition in heat carriers is an urgent task of power engineering and industry sectors. Matrix models of heat transfer based on mass and energy balance equations are applied to solve the inverse problem of heat transfer in heat exchangers, considering the phase transition in heat carriers. A method to calculate and select the designs of multi-threaded heat exchangers, considering the phase transition in heat carriers, has been developed. The author suggests a numerical solution to choose the design of a contact economizer of a heat power plant steam boiler used for heat recovery of flue gases to illustrate the effectiveness of the proposed method. The proposed method to solve the inverse problem of heat transfer provides the possibility to identify simultaneously the most acceptable values of the parameters of heat carriers and design characteristics of heat exchangers for various purposes.

Using CFD Simulations to Improve the Air-Cooled Steam Condenser Performance in Severe Windy Conditions via Proper Tuning of Blades Pitch Angles

2018 ◽  
Author(s):  
Masoud Darbandi ◽  
Hamid Reza Khorshidi Behzadi ◽  
Vahid Farhangmehr ◽  
Gerry E. Schneider
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Power Plants ◽  
Thermal Power ◽  
Research Work ◽  
Convection Heat Transfer ◽  
Heat Rate ◽  
Cost Effective ◽  
Cold Air

The use of air-cooled steam condenser (ACSC) in thermal power plants has become so normal since a few decades ago. It is because there are so many valuable advantages with the ACSC implementation, e.g., little dependency on water consumption and benefiting from the forced convection heat transfer instead of the natural one to condense the steam. However, the thermal performance of an ACSC can be readily defected by the ambient wind; specifically, when the ambient temperature is high. This research work benefits from the computational fluid dynamics tool to study the details of ACSC’s thermal performance in such undesirable ambient windy conditions. Furthermore, this work suggests an effective remedy to increase the heat rate from the proposed ACSC. Evidently, the flow rate of cold air through the heat exchangers of proposed ACSC has direct influence in heat transfer rate from the heat exchangers of ACSC. One remedy to achieve higher cold air flow rates through these heat exchangers is to improve the design of its fans or blowers. However, for an ACSC already in service, one should look for other cost-effective remedies. So, if one wishes to improve the performance of those fans without changing their design one should pay attention to some other simple ways with little costs to implement them. This work suggests to tune up the pitch angles of blades of ACSC’s fans properly. The details of implementing this remedy are presented in this paper.

scholarly journals Matrix method to solve the inverse problem of heat transfer in heat exchangers

Vestnik IGEU ◽  
2021 ◽  
pp. 62-69
Author(s):  
V.P. Zhukov ◽  
A.Ye. Barochkin ◽  
M.S. Bobrova ◽  
A.N. Belyakov ◽  
S.I. Shuvalov
Keyword(s):  
Heat Transfer ◽  
Inverse Problem ◽  
Heat Exchange ◽  
Inverse Problems ◽  
Energy Saving ◽  
Heat Exchangers ◽  
Matrix Method ◽  
Heat Exchange Equipment ◽  
Design Calculations ◽  
Heat Carriers

Along with verification calculations of known designs of heat exchangers, in design engineering and when we develop new technologies, design calculations are necessary to solve the inverse problems of choosing the optimal designs and operating modes of equipment. Previously, the formulation and solution of inverse problems of classification and unsteady heat conduction have been considered, while the inverse problems of heat transfer in the design of heat exchange equipment are poorly presented in the literature. The development of methods to solve inverse problems in the design of heat exchange equipment is an urgent task of power industry. Matrix models of heat transfer based on mass and energy balance equations are used to formulate and solve inverse problems of heat exchange systems. Methods of mathematical programming are applied to solve inverse and optimization problems. For design calculations, a matrix method to solve inverse problems for choosing the design of devices and parameters of heat carriers that ensure the effective operation of the system is proposed. The inverse problem is formulated for the case of the sliding boundary of the beginning of the phase transition with the countercurrent type of movement of heat carriers. The obtained results can be used in power energy, chemical and food industries to improve the efficiency of designing resource-and energy-saving technologies. The solutions obtained can be implemented when developing measures to improve resource and energy saving technologies.

scholarly journals The use of a solution of the inverse heat conduction problem to monitor thermal stresses

2019 ◽  
Vol 108 ◽  
pp. 01003
Author(s):  
Jan Taler ◽  
Piotr Dzierwa ◽  
Magdalena Jaremkiewicz ◽  
Dawid Taler ◽  
Karol Kaczmarski ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Power Plants ◽  
Thermal Stresses ◽  
Thermal Power ◽  
Temperature Fields ◽  
Thick Wall ◽  
Fluid Temperature ◽  
Unsteady Temperature

Thick-wall components of the thermal power unit limit maximum heating and cooling rates during start-up or shut-down of the unit. A method of monitoring the thermal stresses in thick-walled components of thermal power plants is presented. The time variations of the local heat transfer coefficient on the inner surface of the pressure component are determined based on the measurement of the wall temperature at one or six points respectively for one- and three-dimensional unsteady temperature fields in the component. The temperature sensors are located close to the internal surface of the component. A technique for measuring the fastchanging fluid temperature was developed. Thermal stresses in pressure components with complicated shapes can be computed using FEM (Finite Element Method) based on experimentally estimated fluid temperature and heat transfer coefficient

Application of Supercritical Fluids in Thermal- and Nuclear-Power Engineering

2021 ◽  
pp. 601-658
Author(s):  
Igor L. Pioro
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Supercritical Fluids ◽  
Nuclear Power ◽  
Power Plants ◽  
Thermal Power ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Thermal Power Plants ◽  
Power Cycles

Supercritical Fluids (SCFs) have unique thermophyscial properties and heat-transfer characteristics, which make them very attractive for use in power industry. In this chapter, specifics of thermophysical properties and heat transfer of SCFs such as water, carbon dioxide, and helium are considered and discussed. Also, particularities of heat transfer at Supercritical Pressures (SCPs) are presented, and the most accurate heat-transfer correlations are listed. Supercritical Water (SCW) is widely used as the working fluid in the SCP Rankine “steam”-turbine cycle in fossil-fuel thermal power plants. This increase in thermal efficiency is possible by application of high-temperature reactors and power cycles. Currently, six concepts of Generation-IV reactors are being developed, with coolant outlet temperatures of 500°C~1000°C. SCFs will be used as coolants (helium in GFRs and VHTRs, and SCW in SCWRs) and/or working fluids in power cycles (helium, mixture of nitrogen (80%) and helium (20%), nitrogen and carbon dioxide in Brayton gas-turbine cycles, and SCW/“steam” in Rankine cycle).

scholarly journals OTEC Maximum Net Power Output Using Carnot Cycle and Application to Simplify Heat Exchanger Selection

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1143 ◽  
Author(s):  
Kevin Fontaine ◽  
Takeshi Yasunaga ◽  
Yasuyuki Ikegami
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Power Output ◽  
Heat Exchangers ◽  
Power Plants ◽  
Seawater Temperature ◽  
Carnot Cycle ◽  
Ocean Thermal Energy ◽  
Net Power Output

Ocean thermal energy conversion (OTEC) uses the natural thermal gradient in the sea. It has been investigated to make it competitive with conventional power plants, as it has huge potential and can produce energy steadily throughout the year. This has been done mostly by focusing on improving cycle performances or central elements of OTEC, such as heat exchangers. It is difficult to choose a suitable heat exchanger for OTEC with the separate evaluations of the heat transfer coefficient and pressure drop that are usually found in the literature. Accordingly, this paper presents a method to evaluate heat exchangers for OTEC. On the basis of finite-time thermodynamics, the maximum net power output for different heat exchangers using both heat transfer performance and pressure drop was assessed and compared. This method was successfully applied to three heat exchangers. The most suitable heat exchanger was found to lead to a maximum net power output 158% higher than the output of the least suitable heat exchanger. For a difference of 3.7% in the net power output, a difference of 22% in the Reynolds numbers was found. Therefore, those numbers also play a significant role in the choice of heat exchangers as they affect the pumping power required for seawater flowing. A sensitivity analysis showed that seawater temperature does not affect the choice of heat exchangers, even though the net power output was found to decrease by up to 10% with every temperature difference drop of 1 °C.

scholarly journals Review of solid particle materials for heat transfer fluid and thermal energy storage in solar thermal power plants

2019 ◽  
Vol 1 (4) ◽  
Author(s):  
Alejandro Calderón ◽  
Camila Barreneche ◽  
Anabel Palacios ◽  
Mercè Segarra ◽  
Cristina Prieto ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Solid Particle ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Power Plants ◽  
Thermal Power ◽  
Heat Transfer Fluid ◽  
Thermal Power Plants ◽  
Solar Thermal Power
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