scholarly journals COMPARISON OF MATHEMATICAL MODELS FOR HEAT EXCHANGERS OF UNCONVENTIONAL CHP UNITS

2015 ◽  
Vol 55 (4) ◽  
pp. 223 ◽  
Author(s):  
Peter Durcansky
Keyword(s):  
Energy Source ◽  
Heat Exchanger ◽  
Heat Source ◽  
Heat Exchangers ◽  
Primary Energy ◽  
Biomass Combustion ◽  
Cfd Simulations ◽  
Correct Operation ◽  
Hot Air ◽  
Working Medium

An unconventional CHP unit with a hot air engine is designed as the primary energy source with fuel in the form of biomass. The heat source is a furnace designed for combustion of biomass, whether in the form of wood logs or pellets. The transport of energy generated by the biomass combustion to the working medium of a hot-air engine is ensured by a special heat exchanger connected to this resource. The correct operation of the hot-air engine is largely dependent on an appropriate design of the exchanger. The paper deals with the calculation of the heat exchanger for the applications<br />mentioned, using criterion equations, and based on CFD simulations.

Application Study of Newly Developed Turbo Heat Pump for 130 Degrees Celsius Water for an Industrial Process

2011 ◽  
Author(s):  
Shuichi Umezawa ◽  
Haruo Amari ◽  
Hiroyuki Shimada ◽  
Takashi Matsuhisa ◽  
Ryo Fukushima ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Low Temperature ◽  
Heat Source ◽  
Heat Pump ◽  
High Efficiency ◽  
Industrial Process ◽  
Application Study ◽  
Hot Air ◽  
Heat Demand ◽  
Temperature Heat

This paper reports application study of newly developed turbo heat pump for 130 degrees Celsius (°C) water for an industrial process in an actual factory. The heat pump is characterized by high efficiency and large heat output, by using a state-of-the-art turbo compressor. The heat pump requires a low temperature heat source in order to achieve high efficiency. The heat demand is for several drying furnaces in the factory, which requires producing hot air of 120 °C. The heat exchanger was designed to produce the hot air. Experiments were conducted to confirm the performance of the heat exchanger under a reduced size of the heat exchanger. Low temperature heat sources are from both exhaust gas of the drying furnaces and that of an annealing furnace. The heat exchangers were also designed to recover heat of the exhaust gas from the two types of furnace. A thermal storage tank was prepared for the low temperature heat source, and for adjusting the time difference between the heat demand and the low temperature heat source. The size of the tank was determined by considering the schedule of furnaces operations. As a result of the present study, it was confirmed that the heat pump was able to satisfy the present heat demand while retaining high efficiency. Primary energy consumption and CO2 emission of the heat pump were calculated on the basis of the present results in order to compare them with those of the boilers.

scholarly journals  Analysis of rock mass borehole temperatures with vertical heat exchanger

2012 ◽  
Vol 58 (No. 2) ◽  
pp. 57-65 ◽  
Author(s):  
R. Adamovský ◽  
L. Mašek ◽  
P. Neuberger
Keyword(s):  
Energy Source ◽  
Rock Mass ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Heat Extraction ◽  
Heating Season ◽  
Air Temperatures ◽  
Vertical Heat ◽  
Borehole Temperatures

The goal of the article is to analyze the distribution and changes of temperatures in boreholes with the rock mass/fluid tubular heat exchangers used as an energy source for the heat pump. It also aims at documenting changes of temperatures in the rock mass during stagnation and heat extraction, and to compare the temperatures in the active and referential borehole. The testing results showed that temperatures of the rock mass reached a minimal value of 1.3&deg;C at depths of 9 m and 20 m with maximal heat extraction corresponding to minimal air temperatures. The temperatures of the rock mass increased near the end of the heating season to values which correspond to the initial values. The temperature differences of the rock mass between the reference borehole and active boreholes increased to up to 10.5 K during the heating season. However, the temperature differences at the end of the heating season between the reference and active boreholes dropped back to 0.5&ndash;1.1 K. &nbsp;

scholarly journals Exergy analysis of internal regeneration in supercritical cycles of ORC power plant

2012 ◽  
Vol 33 (3) ◽  
pp. 48-60
Author(s):  
Aleksandra Borsukiewicz-Gozdur
Keyword(s):  
Heat Exchanger ◽  
Power Plant ◽  
Heat Source ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Heat Sources ◽  
Regenerative Heat ◽  
Hot Air ◽  
Thermal Oil

Abstract In the paper presented is an idea of organic Rankine cycle (ORC) operating with supercritical parameters and so called dry fluids. Discussed is one of the methods of improving the effectiveness of operation of supercritical cycle by application of internal regeneration of heat through the use of additional heat exchanger. The main objective of internal regenerator is to recover heat from the vapour leaving the turbine and its transfer to the liquid phase of working fluid after the circulation pump. In effect of application of the regenerative heat exchanger it is possible to obtain improved effectiveness of operation of the power plant, however, only in the case when the ORC plant is supplied from the so called sealed heat source. In the present paper presented is the discussion of heat sources and on the base of the case study of two heat sources, namely the rate of heat of thermal oil from the boiler and the rate of heat of hot air from the cooler of the clinkier from the cement production line having the same initial temperature of 260 oC, presented is the influence of the heat source on the justification of application of internal regeneration. In the paper presented are the calculations for the supercritical ORC power plant with R365mfc as a working fluid, accomplished has been exergy changes and exergy efficiency analysis with the view to select the most appropriate parameters of operation of the power plant for given parameters of the heat source.

scholarly journals Particularity of Heat Exchange of Twisted Heat Exchangers in External Flow

2021 ◽  
pp. 12-17
Author(s):  
Valerii Tuz ◽  
Nataliy Lebed ◽  
Maksym Lytvynenko
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Gas Flow ◽  
Annular Channel ◽  
External Flow ◽  
Flow Mode ◽  
Working Medium ◽  
Tubular Surface ◽  
Cold Energy ◽  
Cryogenic Engineering

Perfecting the existing technologies and developing new ones require to rethink the processes in order to obtain qualitatively new results. Widespread use of cryogenic engineering in the chemical industry and medicine calls for a thorough analysis of both the efficiency of thermodynamic cycles and the hardware design of appropriate equipment. The power necessary to obtain low working medium temperatures is distributed between the cooling of the object and the losses in the various elements of the cryogenic setup. One of the best ways to increase the efficiency of the setup is to use the cold energy recovery. This is done by using various designs of recuperative heat exchangers, such as twisted heat exchangers. Existing methods of calculating the parameters of power equipment are based on empirical dependencies, which require some justification and clarification in order to be used for calculating cryogenic equipment parameters. The article describes the experimental setup, presents the research methods applied and analyses the results of the study on convective heat transfer in external flow past the tubular surface of the twisted heat exchanger. The obtained results for the laminar gas flow mode at Re < 2300 allowed determining the length of the initial heat section depending on the regime parameters of the contact phases and the geometric specifications of the twisted heat exchanger. The obtained dependence will make it possible to refine the method of calculating the parameters of the twisted heat exchanger in the annular channel.

Numerical Study of Corrugation Amplitude Influence of a Wavy Fin in Overall Performance of a Compact Heat Exchanger

2014 ◽  
Vol 659 ◽  
pp. 405-410 ◽  
Author(s):  
Vlad Martian ◽  
Septimiu Albetel ◽  
Mihai Nagi
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Numerical Study ◽  
Special Kind ◽  
Cfd Simulations ◽  
Entire Study ◽  
Extended Surface ◽  
Extended Surfaces ◽  
Active Research ◽  
Goodness Factor

In the past few decades heat exchangers, especially air cooled ones, have become very important equipment in different fields of industry. This led to an active research in finding ways to reduce their overall size and costs. A very important role played in reducing the size of the heat exchanger is the convection capability of air, by being the lowest one, dictates the overall size of the heat exchanger. For this reason we are forced to use extended heat transfer surfaces on the air size. The geometry of such extended surfaces has a high impact on heat and pressure drop performances. The present paper focuses on a study, conducted at RAAL S.A. with the support of University “Politehnica” of Timișoara, to find the influence of the corrugation amplitude of a special kind of extended surface named wavy fin, in the overall performances of a heat exchangers by means of area goodness factor (j/f). Designing and building the different geometries needed in the study will be overkill for the company so we have decided to conduct this study with the help of CFD simulations. In order for this to work we will validate the numerical model with the help of a single experimental test, reducing the time and cost of the entire study. These results are afterwards used to modify the fin’s design to obtain an optimum one.

scholarly journals Simulation of Combustion Air Flow in the Gasification Biomass Boiler

2018 ◽  
Vol 168 ◽  
pp. 02015 ◽  
Author(s):  
Marek Patsch ◽  
Peter Pilát
Keyword(s):  
Heat Source ◽  
Air Flow ◽  
Biomass Combustion ◽  
Air Distribution ◽  
Combustion Chambers ◽  
Cfd Simulations ◽  
Piv Measurements ◽  
Biomass Boiler ◽  
Certification Tests ◽  
Experimental Heat

The article deals with the optimization of biomass combustion in a small heat source by means of an optimal distribution of combustion air. The uneven distribution of combustion air has been observed in certification tests and in real operation of used heat source and it has an influence on uneven combustion of biomass in the gasification chamber, on increase emissions and combustion losses. At this stage of the research, optimization of the combustion air distribution is performed by CFD simulations, which will be later verified by PIV measuring of the velocity fields in gasification and combustion chambers of the experimental heat source. CFD simulations and subsequent PIV measurements on the experimental device are realized without real combustion, only the air flow in the empty gasification chamber and in the combustion chamber is investigated. This approach has been chosen to simplify calculations and experiments, and on the assumption that when the combustion air distribution is optimal in empty chambers, it will be optimal even during real combustion. The primary air flow in the gasification chamber is in real operation affected by the size and shape of the inserted biomass and its placement in chamber and this effect is accidental and difficult to verifiable.

Heat Exchanger Analysis Modified to Account for a Heat Source

2007 ◽  
Author(s):  
Vinod Narayanan ◽  
Murty Kanury ◽  
Jeromy Jenks
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Heat Source ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Source Term ◽  
Fluid Stream ◽  
Overall Heat Transfer Coefficient ◽  
Definition Of

The practice of determining the overall heat transfer coefficient using the classical definition of log-mean-temperature-difference in heat exchangers with a heat source term in the hot fluid stream is questioned. The motivation for this work arises from the heat exchanger analysis of an ammonia-water absorber heat exchanger where a heat-of-absorption source term arises in the solution side. A modified heat exchanger analysis is developed here with account for such a heat source. Results of the analysis are discussed and its utility in deducing the overall heat transfer coefficient from experimental measurements is demonstrated.

Inverse Problem Method to Optimize Cascade Heat Exchange Network in Central Heating System

2020 ◽  
Vol 9 (3) ◽  
pp. 62-82
Author(s):  
Yin Zhang ◽  
Yinping Zhang ◽  
Xin Wang
Keyword(s):  
Inverse Problem ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Heat Source ◽  
Heat Exchangers ◽  
Variation Method ◽  
Fluid Temperature ◽  
Central Heating ◽  
Heat Exchange Network ◽  
Exchange Network

In central heating systems, heat is often transferred from heat source to users by the heat network where several heat exchangers are installed at the heat source, substations, and terminals. In this article, the mathematical optimization model of the cascade heat exchange network with three-stage heat exchangers in a series is established. The aim is to maximize the cold fluid temperature for a given hot fluid temperature and overall heating capacity, the optimal heat exchange area distribution, and the medium fluid flow rates are determined through an inverse problem and variation method. The results show that the heat exchange areas should be distributed equally for each heat exchanger. It also indicates that in order to improve the thermal performance of the whole system, more heat exchange areas should be allocated to the heat exchanger where flow rate difference between two fluids is relatively small.

Enabling Batteryless Wearable Devices by Transferring Power Through The Human Body

2021 ◽  
Vol 24 (3) ◽  
pp. 30-34
Author(s):  
Rishi Shukla ◽  
Neev Kiran ◽  
Rui Wang ◽  
Jeremy Gummeson ◽  
Sunghoon Ivan Lee
Keyword(s):  
Energy Source ◽  
Low Power ◽  
Human Body ◽  
Wearable Sensors ◽  
Primary Energy ◽  
Wearable Devices ◽  
Ultra Low Power ◽  
The Past ◽  
Key Barrier

Over the past few decades, we have witnessed tremendous advancements in semiconductor and MEMS technologies, leading to the proliferation of ultra-miniaturized and ultra-low-power (in micro-watt ranges) wearable devices for wellness and healthcare [1]. Most of these wearable sensors are battery powered for their operation. The use of an on-device battery as the primary energy source poses a number of challenges that serve as the key barrier to the development of novel wearable applications and the widespread use of numerous, seamless wearable sensors [5].

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