scholarly journals Numerical modelling of parameters of the operational parameters of an earth-to-air heat exchanger for geothermal ventilation

2020 ◽  
Vol 35 ◽  
pp. 41-48
Author(s):  
O. Nedbailo ◽  
I.. Bozhko ◽  
M. Tkachenko ◽  
S. Andreychuk
Keyword(s):  
Heat Exchanger ◽  
Numerical Model ◽  
Heat Exchangers ◽  
Ventilation System ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Operational Parameters ◽  
National Academy Of Sciences ◽  
Cross Sectional ◽  
Climate Conditions

The aim of this work is to develop a numerical model of the year-round operation of an earth-to-air heat exchanger (EAHE) with a circular cross-sectional shape with further its validation based on the obtained experimental data. We consider that these studies can form the basis for the development of methods for calculating and designing geothermal ventilation systems for climate conditions of Ukraine. The analysis of literature sources showed that now there are quite a lot of studies devoted to the issues of geothermal ventilation. The results of such heat exchanger modeling with various geometric data and which operate in their authentic soils under various hydraulic regimes and that are located at different depths are widely presented. However, these studies do not allow obtaining generalized patterns of heat transfer during the operation of the heat exchangers and the influence of the geometric parameters of the heat exchanger on the operation of the geothermal ventilation system as a whole. Much attention is paid to the issues of modelling the operation of such heat exchangers and the distinctive features of each of these models. Also important are the results of experimental studies carried out on our own experimental bench and with the help of which the numerical model was validated. To conduct experimental research on the operation of the geothermal ventilation system at the Institute of Engineering Thermophysics of the National Academy of Sciences of Ukraine an experimental stand was created. This stand is designed to study thermophysical processes during the operation of a geothermal ventilation system elements. The results of these studies are the basis for the development of a method for determining the optimal diameter of the earth-to-air heat exchanger under operating conditions for soil in Kyiv, Ukraine.

Numerical Modeling and Experimental Studies of the Operational Parameters of the Earth-To-Air Heat Exchanger of the Geothermal Ventilation System

2021 ◽  
Vol 23 ◽  
pp. 42-64
Author(s):  
Boris Basok ◽  
Ihor Bozhko ◽  
Maryna Novitska ◽  
Aleksandr Nedbailo ◽  
Myroslav Tkachenko
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Ventilation System ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Operational Parameters ◽  
Cross Sectional ◽  
Distinctive Features ◽  
Sectional Shape ◽  
Experimental Bench

This article is devoted to the analysis of the heat engineering characteristics of the operation of an Earth-to-Air Heat Exchanger, EAHE, with a circular cross-sectional shape, which is a component of the geothermal ventilation system. The authors analyzed literature sources devoted to the research of heat exchangers of the soil-air type of various designs and for working conditions in various soils. Much attention is paid to the issues of modeling the operation of such heat exchangers and the distinctive features of each of these models. Also important are the results of experimental studies carried out on our own experimental bench and with the help of which the numerical model was validated. The results of these studies are the basis for the development of a method for determining the optimal diameter of an EAHE under operating conditions for soil in Kyiv, Ukraine.

scholarly journals Analytical and Experimental Investigation of a Plate Fin Heat Exchanger at Cryogenics Temperature

2021 ◽  
Vol 39 (4) ◽  
pp. 1225-1235
Author(s):  
Ajay K. Gupta ◽  
Manoj Kumar ◽  
Ranjit K. Sahoo ◽  
Sunil K. Sarangi
Keyword(s):  
Heat Exchanger ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Cryogenic Temperature ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Compact Size

Plate-fin heat exchangers provide a broad range of applications in many cryogenic industries for liquefaction and separation of gasses because of their excellent technical advantages such as high effectiveness, compact size, etc. Correlations are available for the design of a plate-fin heat exchanger, but experimental investigations are few at cryogenic temperature. In the present study, a cryogenic heat exchanger test setup has been designed and fabricated to investigate the performance of plate-fin heat exchanger at cryogenic temperature. Major parameters (Colburn factor, Friction factor, etc.) that affect the performance of plate-fin heat exchangers are provided concisely. The effect of mass flow rate and inlet temperature on the effectiveness and pressure drop of the heat exchanger are investigated. It is observed that with an increase in mass flow rate effectiveness and pressure drop increases. The present setup emphasis the systematic procedure to perform the experiment based on cryogenic operating conditions and represent its uncertainties level.

scholarly journals Environmental Characteristics of Modern Systems of Domestic Use of Fuel. Part 2. Pollutants Formation by Natural Gas Combustion in Atmospheric Burners: Experimental Studies

2020 ◽  
Vol 63 (5) ◽  
pp. 450-461
Author(s):  
B. S. Soroka ◽  
V. V. Horupa
Keyword(s):  
Thermal Power ◽  
Experimental Studies ◽  
Environmental Indicators ◽  
Gas Pressure ◽  
Operating Conditions ◽  
National Academy Of Sciences ◽  
High Concentration ◽  
Hydrocarbon Gases ◽  
Absolute Level ◽  
Toxic Emissions

The Gas Institute of the National Academy of Sciences of Ukraine performs comprehensive studies of the formation of toxic emissions in the flame of atmospheric burners and beyond the visible burning cones (“rich” primary flame). The experiments are based on the proven significant content of harmful substances in the combustion products of gas fuel in household appliances and on direct contact of consumers with gas emissions during the operation of the stoves. A methodology for the experimental researches of the harmful emissions formation has been proposed while the computerized firing rig serving as the diagnostic facility has been developed for studying the combustion of hydrocarbon gases in the burners of household stoves. Carbon oxides CO and nitrogen oxides NO and NO2 are considered as toxic emissions, while the primary air excess coefficient and the heat load of the burner are considered as variable parameters. Under operating conditions of a gas stove, its variable characteristics are the gas pressure in front of the nozzle of the atmospheric burner and its thermal power. When optimizing the design of burners, the determinant value of the stability of burning, energy and environmental indicators of fuel combustion is the coefficient of excess of primary air λpr at a given gas pressure before the burner. The influence of this coefficient on the formation of CO, NO, NO2 is established, and the possibility of emissions with a high concentration of nitrogen dioxide is proved. Since the concentration of [NO] decreases with an increase in λpr, and the absolute level of [NO2] concentrations is not significantly affected by the value of λpr, it is determined that the proportion of [NO2] concentration in the [NOx] = [NO] + [NO2] compound increases with an increase in the primary air excess coefficient.

scholarly journals Experimental Study for Counter to Cross Flow Air-cooled Heat Exchangerof Annular Tube having Internal Circular grooving at Different pitches - A Review

2020 ◽  
pp. 268-274
Author(s):  
Suneel Nagar ◽  
Ajay Singh ◽  
Deepak Patel
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Operating Conditions ◽  
Theory And Practice ◽  
Thermal Flow ◽  
Total Cost ◽  
Literature Theory ◽  
Modern Analytical ◽  
Annular Tube

The objective of this study is to provide modern analytical and empirical tools for evaluation of the thermal-flow performance or design of air-cooled heat exchangers (ACHE) and cooling towers. This review consist various factors which effect the performance of ACHE. We introduced systematically to the literature, theory, and practice relevant to the performance evaluation and design of industrial cooling. Its provide better understanding of the performance characteristics of a heat exchanger, effectiveness can be improved in different operating conditions .The total cost of cycle can be reduced by increasing the effectiveness of heat exchanger.

Influence of the Pressure Load in the Efficiency of a Longitudinal Ventilation System in Road Tunnels

2009 ◽  
Author(s):  
Mo´nica Galdo-Vega ◽  
Carlos Santolaria-Morros ◽  
Jesu´s Manuel Ferna´ndez Oro ◽  
Katia Maria Argu¨elles-Di´az
Keyword(s):  
Momentum Transfer ◽  
Ventilation System ◽  
Operating Conditions ◽  
Traffic Density ◽  
Moderate Pressure ◽  
Pressure Gradients ◽  
Operational Parameters ◽  
Satisfactory Description ◽  
Longitudinal Ventilation ◽  
Road Tunnels

The longitudinal ventilation system (LVS) efficiency in road tunnels is conditioned by geometric and operational parameters. Typical geometric parameters are the length of the tunnel, its slope and the transversal section. All these factors are generally fixed and thus not modifiable in the regular operation of the facility. On the other hand, operational parameters, like the working fans layout, the environmental conditions or the traffic density are case-sensitive and susceptible to influence the baseline performance of the ventilation system. In the present study, different pressure gradients, established between inlet and outlet location of the jet fan influence, are analyzed. This static resistance is shown to have a significant impact on the momentum transfer established between the jet expansion and the bulk flow inside the tunnel. For moderate pressure gradients, the jet discharged from fan is relativity well-mixed, allowing to reach uniform flow conditions in the streamwise direction. When the adverse pressure gradients become severe, the high-velocity flow is blocked, unable to mix out in the inter fan spacing and losing spanwise uniformity. At critical conditions, large recirculation areas can be developed within primary flow structures, generating turbulence and important energy losses, and even inducing reverse flow at the tunnel exit. The extreme operating conditions of a longitudinal ventilation system in a road tunnel have been studied using a 3D numerical simulation. Preliminary analysis for grid sensitivity and election of an accurate turbulence closure were performed to guarantee a valuable modeling. Following, systematic computations over a cluster of PC’s were executed using the well-tested Fluent code. RANS modeling with RSM scheme allowed a satisfactory description of three-dimensional vortical structure in the recirculation zones, especially for adverse pressure gradients. At this point, numerical results have provided a comprehensive overview of the mechanism associated to the momentum transfer of the jet expansion, comparing the performance for zero-pressure gradients with those observed for adverse conditions. Also, this paper gives valuable information about practical limits of the LVS, advancing operational conditions that compromise the ventilation efficiency.

The Effect of Geometrical Features on Air-Side Heat Transfer and Friction Characteristics, and Optimization of a Large-Size Plain Fin-and-Tube Heat Exchanger by 3-D Numerical Simulation

2009 ◽  
Author(s):  
M. Izadi ◽  
D. K. Aidun ◽  
P. Marzocca ◽  
H. Lee
Keyword(s):  
Heat Transfer ◽  
Numerical Modeling ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Simple Algorithm ◽  
Operating Conditions ◽  
Friction Characteristics ◽  
Tube Heat Exchanger ◽  
Large Size ◽  
Geometrical Features

The effect of geometrical features on the air-side heat transfer and friction characteristics of an industrial plain fin-and-tube heat exchanger is investigated by 3-D numerical modeling and simulations. The heat exchanger has been designed and employed as an intercooler in a gas power plant and is a large-size compact heat exchanger. Most of the available design correlations developed so far for plain fin–and–tube heat exchangers have been prepared for small-size exchangers and none of them fits completely to the current heat exchanger regarding the geometrical limitations of correlations. It is shown that neglecting these limitations and applying improper correlations may generate considerable amount of error in the design of such a large-size heat exchanger. The geometry required for numerical modeling is produced by Gambit® software and the boundary conditions are defined regarding the real operating conditions. Then, three-dimensional simulations based on the SIMPLE algorithm in laminar flow regime are performed by FLUENT™ code. The effect of fin pitch, tube pitch, and tube diameter on the thermo-hydraulic behavior of the heat exchanger is studied. Some variations in the design of the heat exchanger are suggested for optimization purposes. It is finally concluded that the current numerical model is a powerful tool to design and optimize of large-size plain fin-and-tube heat exchangers with acceptable accuracy.

scholarly journals An Experimentally Validated Numerical Modeling Technique for Perforated Plate Heat Exchangers

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
M. J. White ◽  
G. F. Nellis ◽  
S. A. Klein ◽  
W. Zhu ◽  
Y. Gianchandani
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Model ◽  
Heat Exchangers ◽  
Perforated Plate ◽  
Plate Heat Exchanger ◽  
Internal Temperature ◽  
Perforated Plates ◽  
Axial Conduction ◽  
Plate Heat

Cryogenic and high-temperature systems often require compact heat exchangers with a high resistance to axial conduction in order to control the heat transfer induced by axial temperature differences. One attractive design for such applications is a perforated plate heat exchanger that utilizes high conductivity perforated plates to provide the stream-to-stream heat transfer and low conductivity spacers to prevent axial conduction between the perforated plates. This paper presents a numerical model of a perforated plate heat exchanger that accounts for axial conduction, external parasitic heat loads, variable fluid and material properties, and conduction to and from the ends of the heat exchanger. The numerical model is validated by experimentally testing several perforated plate heat exchangers that are fabricated using microelectromechanical systems based manufacturing methods. This type of heat exchanger was investigated for potential use in a cryosurgical probe. One of these heat exchangers included perforated plates with integrated platinum resistance thermometers. These plates provided in situ measurements of the internal temperature distribution in addition to the temperature, pressure, and flow rate measured at the inlet and exit ports of the device. The platinum wires were deposited between the fluid passages on the perforated plate and are used to measure the temperature at the interface between the wall material and the flowing fluid. The experimental testing demonstrates the ability of the numerical model to accurately predict both the overall performance and the internal temperature distribution of perforated plate heat exchangers over a range of geometry and operating conditions. The parameters that were varied include the axial length, temperature range, mass flow rate, and working fluid.

Thermal Analysis Technique for Coolers Operating in Off and Low Load Conditions

2012 ◽  
Author(s):  
Thomas J. Muldoon
Keyword(s):  
Heat Exchanger ◽  
Power Plant ◽  
Heat Exchangers ◽  
Cooling Water ◽  
Control Valve ◽  
Operating Conditions ◽  
Outlet Temperature ◽  
Inlet Valve ◽  
Plant Personnel ◽  
Load Conditions

The most conservatively designed power plant heat exchangers are designed to meet a maximum heat load with minimum fluid temperature differences. When the input temperatures are less than design maximums, the cooler will usually be in a position of over performance. This relationship is especially true when the heat exchanger is a closed Component Cooling Water (CCW) heat exchanger with inlet fluid at ambient conditions. Maintaining a consistent cooling temperature is an important concern in the operation of a power plant. It is important that the cooling needs of the equipment such as the hydrogen coolers are maintained at a set temperature. Overcooling may not be of benefit to the equipment. The component which cools the service water with the local cooling water is a component cooling water heat exchanger (CCW). The two primary methods of controlling the heat rejection performance on these vessels is to throttling the tubeside flow to get a consistent shell outlet temperature with control valves or leave the tubeside flow constant and by-pass a portion of the shellside flow. Estimating the performance of the heat exchanger with given set of inlet conditions and a fixed design point can be accomplished using a the Number Transfer Units (NTU) method. Opening and closing the control valve is based on the estimated performance. This analysis can be used by power plant personnel to gauge the operation of these vessels over varying operating conditions. The analysis can also include the effect of different values of cleanliness and the extent of throttling. As a unit experiences fouling, additional flow is required to meet the thermal requirements. Depending upon the extent of fouling, the inlet valve will be either opened or closed. Plant personnel may observe the cooling water inlet temperature and the extent to which the inlet valve is open, and use that information to determine possible fouling and setup a maintenance schedule. The following analytical approach for evaluating low, critical, or off load conditions is important in the design and operation of these types of power plant heat exchangers, piping and control valve systems.

Novel Evaporator Geometries Based on Entrance-Length Flow-Paths for Geothermal Binary Power Plants

2016 ◽  
Author(s):  
Adrian S. Sabau ◽  
Ali H. Nejad ◽  
James W. Klett ◽  
Adrian Bejan ◽  
Kivanc Ekici
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
Cost Model ◽  
Operating Conditions ◽  
Transfer Model ◽  
Length Scale ◽  
Entrance Length ◽  
Scale Levels

In this paper, a novel geometry is proposed for evaporators that are used in Organic Rankine Cycles. The proposed geometry consists of employing successive plenums at several length-scale levels, creating a multi-scale heat exchanger. The channels at the lowest length-scale levels were considered to have their length given by the thermal entrance-length. Numerical simulations based on turbulent flow correlations for supercritical R134a and water were used to obtain performance indicators for new heat exchangers and baseline heat exchangers. The relationship between the size of the channels at one level, k, with respect to the size of the channels at the next level, k + 1, is based on generalization of the “Murray’s law.” In order to account for the variation of the temperature and heat transfer coefficient in the entrance region, a heat transfer model was developed. The variation of the brine and refrigerant temperatures along each pipe was considered. Using the data on pumping power and weight of metal structures, including that of all the plenums and piping, the total present cost was evaluated using a cost model for shell-and-tube heat exchangers. In addition to the total present cost, the data on overall thermal resistance is also used in identifying optimal heat exchanger configurations. The main design variables include: tube arrangement, number of channels fed from plenum, and number of rows in the tube bank seen by the outside fluid. In order to assess the potential improvement of the new evaporator designs, baseline evaporators were designed. The baseline evaporator designs include long tubes of the same diameter as those of the lowest length-scale levels, placed between one inlet and one outlet. The baseline evaporator designs were created from the new evaporator designs by simply removing most of the internal plenums employing tubes much longer than their entrance length, as they would currently be used. Consistent with geothermal applications, the performance of new heat exchanger designs was compared to that of baseline heat exchanger designs at the same flow rates. For some operating conditions it was found that the new heat exchangers outperform their corresponding baseline heat exchangers.

scholarly journals Horizontal earth-air heat exchanger for preheating external air in the mechanical ventilation system

2018 ◽  
Vol 13 (1) ◽  
pp. 71-76
Author(s):  
Vasyl Zhelykh ◽  
Olena Savchenko ◽  
Vadym Matusevych
Keyword(s):  
Heat Transfer ◽  
Mechanical Ventilation ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Heat Exchangers ◽  
Convective Heat Transfer Coefficient ◽  
Ventilation System ◽  
Heat Pipes ◽  
Heat Exchanger Tube ◽  
Exchanger Tube

Abstract To save traditional energy sources in mechanical ventilation systems, it is advisable to use low-energy ground energy for preheating or cooling the outside air. Heat exchange between ground and outside air occurs in ground heat exchangers. Many factors influence the process of heat transfer between air in the heat exchanger and the ground, in particular geological and climatic parameters of the construction site, parameters of the ventilation air in the projected house, physical and geometric parameters of the heat exchanger tube. Part of the parameters when designing a ventilation system with earth-air heat exchangers couldn’t be changed. The one of the factors, the change which directly affects the process of heat transfer between ground and air, is convective heat transfer coefficient from the internal surface of the heat exchanger tube. In this article the designs of a horizontal earthair heat exchanger with heat pipes was proposed. The use of heat pipes in designs of a horizontal heat exchanger allows intensification of the process of heat exchange by turbulence of air flow inside the heat exchanger. Besides this, additionally heat transfer from the ground to the air is carried out at the expense of heat transfer in the heat pipe itself.

Sign in / Sign up

Export Citation Format

Share Document