heat losses
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Author(s):  
Vassilios E. Papadopoulos ◽  
Ioanna N. Kefala ◽  
Georgia D. Kaprou ◽  
Angeliki Tserepi ◽  
George Kokkoris

2022 ◽  
Vol 24 (4) ◽  
pp. 13-18
Author(s):  
Dmitriy S. Klyuev ◽  
Yulia V. Sokolova

A singular integral equation for an electric dipole has been obtained, which makes it possible to take into account the finite conductivity of the metal from which it is made. The derivation of the singular integral equation is based on the application of the Greens function for free space, written in a cylindrical coordinate system, taking into account the absence of the dependence of the field on the azimuthal coordinate, on a point source located on the surface of an electric dipole. Methods for its solution are proposed. In contrast to the well-known mathematical models of an electric dipole, built in the approximation of an ideal conductor, the use of the singular integral equation obtained in this work makes it possible to take into account heat losses and calculate the efficiency.


2022 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Z. Ebrahimpour ◽  
Seyyed Ali Farshad ◽  
M. Sheikholeslami

Purpose This paper scrutinizes exergy loss and hydrothermal analysis of Linear Fresnel Reflector (LFR) unit by means of FLUENT. Several mirrors were used to guide the solar radiation inside the receiver, which has parabolic shape. Radiation model was used to simulate radiation mode. Design/methodology/approach Heat losses from receiver should be minimized to reach the optimized design. Outputs were summarized as contours of incident radiation, isotherm and streamline. Outputs were classified in terms of contours and plots to depict the influence of temperature of hot wall, wind velocity and configurations on performance of Linear Fresnel Reflector (LFR) based on thermal and exergy treatment. Four arrangements for LFR units are considered and all of them have same height. Findings Greatest Nu and Ex can be obtained for case D due to the highest heat loss from hot wall. Share of radiative heat flux relative to total heat flux is about 94% for case D. In case D when Tr = 0.388, As hext rises from 5 to 20, Nutotal enhances about 11.42% when Tr = 0.388. By selecting case D instead of case A, Ex rises about 16.14% for lowest Tr. Nutotal and Ex of case D augment by 3.65 and 6.23 times with rise of Tr when hext = 5. To evaluate the thermal performance (ηth) of system, absorber pipe was inserted below the parabolic reflector and 12 mirrors were used above the ground. The outputs revealed that ηth decreases about 14.31% and 2.54% with augment of Tin and Q if other factors are minimum. Originality value This paper scrutinizes exergy loss and hydrothermal analysis of LFR unit by means of finite volume method. Several mirror used to guide the solar radiation inside the receiver, which has parabolic shape. DO model was used to simulate radiation mode. Heat losses from receiver should be minimized to reach the optimized design. Outputs were summarized as contours of incident radiation, isotherm and streamline.


2022 ◽  
Vol 933 ◽  
Author(s):  
Enrique Flores-Montoya ◽  
Victor Muntean ◽  
Mario Sánchez-Sanz ◽  
Daniel Martínez-Ruiz

This paper presents an experimental study of the influence of heat losses on the onset of thermoacoustic instabilities in methane–air premixed flames propagating in a horizontal tube of diameter, $D = 10$ mm. Flames are ignited at the open end of the tube and propagate towards the closed end undergoing strong oscillations of different features owing to the interaction with acoustic waves. The frequency of oscillation and its axial location are controlled through the tube length $L$ and the intensity of heat losses. These parameters are respectively modified in the experiments by a moveable piston and a circulating thermal bath of water prescribing temperature conditions. Main experimental observations show that classical one-dimensional predictions of the oscillation frequency do not accurately describe the phenomena under non-adiabatic real scenarios. In addition to the experimental measurements, a quasi-one-dimensional analysis of the burnt gases is provided, which introduces the effect of heat losses at the wall of the tube on the interplay between the acoustic field and the reaction sheet. As a result, this analysis provides an improved description of the interaction and accurately predicts the excited flame-oscillation harmonics through the eigenvalues of the non-adiabatic acoustics model. Unlike the original one-dimensional analysis, the comparison between the flame oscillation frequency provided by the non-adiabatic extended theory and the frequencies measured in our experiments is in excellent agreement in the whole range of temperatures considered. This confirms the importance of heat losses in the modulation of the instabilities and the transition between different flame oscillation regimes.


2022 ◽  
Vol 1211 (1) ◽  
pp. 012019
Author(s):  
T M Khalina ◽  
M V Khalin ◽  
M V Dorozhkin

Abstract The article is dedicated to the study of the heat transfer processes that occur in the feedstuff disinfection chamber that relies upon electric contact heating. The mechanism of the temperature gradient appearance, which is the main cause of the heat losses has been investigated. The basic equations of heat conduction are considered. A method is proposed for determining the key parameters of the heat transfer process. A functional diagram of the experimental setup with a description of the operation of individual units is presented. The dependence for the transient operating mode of the unit on the growth of heat losses has been established. Thermal images of different shapes of the unit dielectric chambers have been provided as well as temperature field distribution through the chamber wall.


2022 ◽  
Vol 2163 (1) ◽  
pp. 012005
Author(s):  
G Guerrero Gómez ◽  
N Afanador Garcia ◽  
C Nolasco Serna

Abstract The recording of temperatures in different positions in the firing process in an intermittent kiln to produce ceramic materials is presented, which led to the energy evaluation, determining the heat used for the clay firing process and the heat losses. In addition, a study of the emissions of pollutant gases released into the environment was carried out, as stipulated in the protocol of control, and monitoring of stationary source. In the energy balance, large energy losses were detected in heat accumulation in the masonry of 7.20×106 KJ of the energy supplied, representing 16.99%, and in the kiln walls of 5.20×10 KJ, representing 12.17%. As a result, it is necessary to make constructive and operative changes in the operation of the kilns, which will lead to the recovery of residual heat in the use of drying of parts, drying, and preheating of combustion air, reducing energy consumption and emissions of pollutants into the atmosphere. The average concentration of particulate matter released into the environment was 1056.60 mg/m3, 422% higher than the standard, affecting people’s health.


Author(s):  
Vladimir Demchenko ◽  
Alina Konyk ◽  
Vladimir Falko

The article is devoted to topical issues related to the storage, accumulation and transportation of heat by stationary and mobile heat storage. Analysis of the current state of the district heating system indicates significant heat losses at all stages of providing the consumer with heat. The use of heat storage in heat supply systems leads to balancing the heat supply system, namely, the peak load is reduced; heat production schedules are optimized by accumulating excess energy and using it during emergency outages; heat losses caused by uneven operation of thermal equipment during heat generation are reduced; the need for primary energy and fuel consumption is reduced, as well as the amount of harmful emissions into the environment. The main focus is on mobile thermal batteries (M-TES). The use of M-TES makes it possible to build a completely new discrete heat supply system without the traditional pipeline transport of the heat carrier. The defining parameters affecting the efficiency of the M-TES are the reliability and convenience of the design, the efficiency and volume of the “working fluid”, the operating temperature of the MTA recharging and the distance of transportation from the heat source to the consumer. The article contains examples of the implementation of mobile heat accumulators in the world and in Ukraine, their technical and technological characteristics, scope and degree of efficiency. The technical indicators of the implemented project for the creation of a mobile heat accumulator located in a 20-foot container and intended for transportation by any available means of transport are given.


Author(s):  
Marina Savchenko-Pererva ◽  
Oleg Radchuk ◽  
Ludmila Rozhkova ◽  
Hanna Barsukova ◽  
Oleksandr Savoiskyi

This paper gives examples of the implementation of energy-saving measures in public premises. The introduction of energy-saving measures at enterprises significantly reduces the fixed component of industrial expenditures. As a rule, educational institutions, for example, public premises, are financed from the state budget, and saving money on utilities will enable redirecting finances to the development of the university’s educational and scientific base. Thus, the main purpose of implementing such measures is to reduce the cost of maintaining buildings. The measures are divided into three stages. At the first preparatory stage, the problem elements of a building and communications, which require the introduction of energy-saving measures using a special Fluke Ti25 device, are identified. Problem elements of the building structure were determined by complete scanning of the ceiling, walls, and floor with the help of a thermal imager. A large (more than 10 %) difference between indoor air temperature and the temperature of the building element indicates a problem element. The research method is thermographic. The study contains an example of scanning the wall of the premises. The temperature difference between the left and the right sides of the wall is 2.6 °C (the difference with the room temperature is 21 %). This indicates significant heat losses through the wall. At the second stage of information processing, measures to reduce energy consumption were determined. At the third stage of the introduction of energy-saving measures, the measures that directly affect the energy consumption of a building and effective functioning of communications were implemented. The practical relevance of the study is to obtain results and practical recommendations that can be applied in practice to improve the energy efficiency of premises and buildings.


Author(s):  
Alexander Aleksakhin ◽  
Iryna Dubynskaya ◽  
Ilona Solyanyk ◽  
Zhanna Dombrovs’ka

Heat losses at the heating network’s distribution pipelines were identified for Karkivcommunity. Heat losses’ calculation is performed in view of the underground pipelines’ installationin non-accessible ducts. The heating system water temperature is accepted in line with the heatingnetwork temperature chart and according to the design outdoor temperature value for heatingpurposes. Specific heat losses in the network section’ pipelines are accepted at the level of standardvalues for the specified network laying method. The water flow rate at the heat pipeline sections isdefined as per the design heat loads from the buildings connected to the heat supply network. Theheat pipeline segment with uniform diameter is accepted as the rated section. The soil temperatureat the heat pipeline axis laying depth is accepted as 5°C. The heat losses at the structural networkelements are considered by 1.15 coefficient. The calculations are performed in view of the heatingsystem water flow rate and temperate changes along the heat pipeline length. While analyzing thethermal condition of the return pipelines of the community heating network, the changes in the heatcontent of the heating system water flow in the main direction pipeline during mixing with the waterflow from the branches of the main direction line are taken into account. Considering the averagetemperature of the coldest five days consecutively, the total energy loss in heating pipeline for a groupof buildings in Kharkov region are equivalent to 180.8kW.In view of the ambient air temperature changing over the heating period for Kharkiv cityclimate conditions and the current schedule for quality heat energy supply to the consumers controlthe annual heat losses in the community heating network pipelines were calculated. The soil temperature change at the heat pipeline installation depth during the heating period was notconsidered.Heat losses in the microdistrict network for the year are 2184 GJ. The data obtained can beused to compare options when developing a strategy for reforming the microdistrict heat supplysystem.


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