Учебное пособие 2132

ISSN 2542-0526

RUSSIAN JOURNAL

OF BUILDING

CONSTRUCTION AND ARCHITECTURE

N 2 (42)

BUILDING STRUCTURES, BUILDINGS AND CONSTRUCTIONS

BASES AND FOUNDATIONS, UNDERGROUND STRUCTURES

HEAT AND GAS SUPPLY, VENTILATION, AIR CONDITIONING, GAS SUPPLY AND ILLUMINATION

BUILDING MATERIALS AND PRODUCTS

TECHNOLOGY AND ORGANIZATION OF CONSTRUCTION

DESIGNING AND CONSTRUCTION OF ROADS, SUBWAYS, AIRFIELDS, BRIDGES AND TRANSPORT TUNNELS

BUILDING MECHANICS

THEORY AND HISTORY OF ARCHITECTURE, RESTORATION AND RECONSTRUCTION OF HISTORICAL

AND ARCHITECTURAL HERITAGE

ARCHITECTURE OF BUILDINGS AND STRUCTURES. CREATIVE CONCEPTIONS OF ARCHITECTURAL ACTIVITY

CITY PLANNING, PLANNING OF VILLAGE SETTLEMENTS

Voronezh 2019

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Russian Journal

of Building Construction and Architecture

Periodical scientific edition

Founder and publisher: Federal State Education Budget Institution of Higher Professional Education «Voronezh State Technical University».

The articles are reviewed and processed with the program ANTIPLAGIARISM. This publication cannot be reprinted without the prior permission of the publisher, references are obligatory.

Number of the certificate of registration of the media ПИ №ФС 77-67855 Issued bythe Federal Service for Supervision of Communications, Information Technology,

and Mass Media (Roskomnadzor)

Price is subject tochange

EDITORIAL COUNCIL

The Head of the Council: Kolodyazhny S. A., D. Sc. in Engineering, rector (Voronezh State Technical University)

EDITORIAL BOARD

Editor-in-Chief: Melkumov V. N., D. Sc. in Engineering, Prof.

(Voronezh State Technical University)

Members:

THE ADDRESS of EDITORIAL AND THE PUBLISHER OFFICE:84 20-letiya Oktyabrya str., Voronezh, 394006, Russian Federation Tel./fax: (473)2-774-006; e-mail: vestnik_vgasu@mail.ru

Publication date 15.05.2019. Format 60×84 1/8. Conventional printed sheets 12. Circulation 500 copies. Order 87 .

Published in Printing Office of Voronezh State Technical University 84 20-letiya Oktyabrya str., Voronezh, 394006, Russian Federation

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HEAT AND GAS SUPPLY, VENTILATION, AIR CONDITIONING,

GAS SUPPLY AND ILLUMINATION

DOI 10.25987/VSTU.2019.42.2.001

UDC 697.9

V. A. Gulevskii1, Ye. N. Osipov2, V. P. Shatskii3

COOLING OF TECHNICAL OBJECTS USING EVAPORATION COOLERS

Voronezh State Agricultural University

Russia, Voronezh, tel: (473)29-103-39, e-mail: sha.vladim@yandex.ru

1D. Sc. in Engineering, Prof. of the Dept. of Mathematics and Physics

2PhD student of the Dept. of Mathematics and Physics

3D. Sc. in Engineering, Head of the Dept. of Mathematics and Physics

Statement of the problem. The problem of air cooling of technical objects by means of evaporative recuperative coolers is considered.

Results. The equation of an unsteady thermal balance of limited volume with technological equipment is derived taking into account its cooling by recuperative water-evaporative coolers. The mathematical model of thermal and physical processes in indirect evaporative recuperative air coolers and the method of its implementation are presented. The model contains partial differential equations describing the energyand mass transfer in the channels of the heat exchange unit.

Conclusions. As a result of the research, it was established that installing indirect evaporative recuperative cooling of type will allow one without increasing the humiditylevel of the air yto considerablyreduce the temperature in facilities with technological equipment emitting a great deal of heat. Environmental friendliness and cost effectiveness of cooling units of this type add to the positive effects theyoffer.

Keywords: evaporative coolers, mathematical modeling, heat balance, industrial facility.

Introduction. The lack of energy resources and impending environmental pollution are paving the way for sustainable energy technologies and renewable energy sources. One of the areas of technology that is currently in demand is reducing the air temperature of facilities equipped with large air emission sources. Ventilation systems of traction substations, engine rooms of metropolitan stations do not warrant a proper temperature due to a lot of incoming air from the equipment and limited volumes of supplied air. In this case heat can only be utilized provided that a variety of air conditioning setups is employed.

© Gulevskii V. A., Osipov Ye. N., Shatskii V. P., 2019

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Water vapour coolers that have been in use over the recent decades have proved to be reliable, high-performance and environmentally friendly. Among other things, cooling commonly involves high humidity levels of the incoming air, which is not permissible in metro stations. Therefore designing indirect recuperative water vapour coolers that are capable of air cooling with no changes in its humidity level is an important issue.

1.Choosing the air cooling method. Compressor systems using freon or substitutes are not particularly energy-saving and most importantly, they not only produce cold but also emit a great deal of heat that might be challenging to deflect in small spaces. Therefore using air-cooling equipment that doesnot contribute to higher humidity levels seems more appropriate to use.

The principle of the operation of indirect recuperative vapour is as follows. A common air flux is fed not into layers not coming into contact with water “dry” channel s where this flux is split into the “main” one coming into the facility and the “auxiliary” one that is in the opposite direction and coming into alternating “dry” and “wet” channel s where water is evaporated off capillary and porous surfaces splitting the channel s of plates. This moist air cools down the “main” air flux by means of heat transfer and is deflected beyond the facility.

The major advantages of the setups are the following: –– World-class environmental safety;

–– Comfort and safety of the output air in terms of flu and cold bugs;

–– Use ofthe block method which makesdesign, assemblyand maintenanceconsiderablyeasier; –– Easy-to-use operation, no special equipment or materials required;

–– 3––5 times energy savings;

–– Self-regulation effect (depending on the air parameters), which makes the system a lot easier to use and saves automatization costs.

Starting fromthe late 2007 air coolersАОВ-5000 [1] have been in operation in the transformation stations (TS) of the Moscow metro system. They are particularly designed for temperature of the channel. Their cooling principle entails the main air flux fed into a special collector below the transformers which then passes through them taking off their heat. The auxiliary air flux is deflected from the TS into the tunnel through air deflectors. Owing to the scheme and high performance ofthe coolersthe temperature inthe TS wasreduced from380Сdownto 270С.

2.Modelling a heat balance and physical processes in indirect recuperative water vapours. In order to identify operating modes of coolers, it is necessary that we carry out mathematical modeling of heat balance of in the cooling facility with consideration of the above cooling system.

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Russian Journal of Building Construction and Architecture

Let the initial temperatures of the enclosures of the premises be T0 = const. At the time moment t = 0 its surface starts washing a gaseous surface with the temperature T(τ). Heat ex change between the environment and a semi-infinite surface of the enclosures complies with the Newton law (the third-order boundary condition). Let us look at the heat balance in the cooling facility (Fig. 1).

Fig. 1. For identifying the heat balance equation.

Q are heat emissions of the equipment, q is the heat flux through the enclosures, G is the total air flux of the temperature T at the cooler input, Gm = Ginf are the fluxes of the “wet” air and infiltration air

ofthetemperatureТn,Gs andТk istheconsumption andtemperatureofthe“dry” airatthecooler outputrespectively

Over the time change in the energy V is given by the formula:

Q1 C V T T .

The energy Q comes from the equipment. Due to the general air flux coming into the cool-

sumption of the auxiliary air flux.

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There is heat exchange through the walls with the energy Q5 q Fogr where q is the density of the heat flux [2, 8, 9, 15]:

u is the speed of the blown air, m/seс, λ is the coefficient of the heat conchannel ivity of the

x

erf(x) 2 e 2d is the Gauss error function, or a probability integral.

0

The equation of heat balance is as follows:

Q1 Q Q2 Q3 Q4 Q5 .

Inserting the previous ratios into the last equation and moving on to the range at 0, weget:

C V dT( ) Q C GT( ) C GkTk ( ) C GinfTn d

T( ) T0 eH2a erfc(Ha )Fogr.

Let us denote as k the ratio of the main air flux Gk to the auxiliary one Gm. Then G= Gm + + Gk = (k+1) Gm and

C V dT( ) Q C (k 1) GmT( ) C Gm (kTk ( ) Tn ) d

T T0 eH2a erfc(Ha ) Fogr.

or

T T0 eH2a erfc(Ha ) Fogr /C .

Adding the original condition: T 0 Tнач , we get the Koshi task for determining the dependence of the air temperature in the facility on the time.

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