RU2246671C1 - Evaporator-condenser - Google Patents

Abstract

FIELD: heat-exchange apparatuses of refrigerating plants.

SUBSTANCE: the evaporative condenser has a metal body the evaporative condenser has a metal body with a turbo bunch, finned plates, nozzles, fan located in it. A high-voltage positive-charged electrode is installed isolately from the body after the nozzles, and with the other end it is fastened on the tube bunch with the @minus@ sign. The high-voltage electrode is made in the form of a metal net carrying metal needles welded to the base of the high-voltage electrode opposite each nozzle.

EFFECT: enhanced heat extraction from the surface of tubes, in which cooling medium is circulating, reduced water consumption, reduced duration of the process, provided preventum of evaporator fouling.

2 cl, 2 dwg

Description

The invention relates to heat exchangers of refrigeration units and can be used as an air-evaporative condenser of refrigeration machines.

Known evaporative cooler comprising a housing with a tray in the lower part with pipes inside provided with transverse ribs [1]. To intensify heat transfer, the fins are made in the form of panels, installed in pairs with a predetermined pitch along the pipes with the formation of slotted channels connected by a lower end to the pallet.

The upper end of the channels is equipped with a film former.

The operation of the cooler is as follows. Fan air is drawn in through the windows. Water is pumped countercurrently from the sump through the slotted channels.

The water flow is regulated in such a way as to provide a continuous film of the required thickness on the outer surface of the channels without gushing at their upper end of the water jets.

A film of water flowing down the outer surface of the channels evaporates during heat and mass transfer with air moving countercurrently, while taking heat from the surface of the pipes inside which the cooled medium circulates.

The disadvantage of these coolers is insufficient intensification of heat and mass transfer due to the slow evaporation of a film of water flowing down the outer surface of the channels.

Known invention [2]. To intensify heat transfer, the cooler contains a system of perforated pipes with open ends for the passage of freshly saturated air located inside the tube bundle.

The cooler comprises a housing with an irrigation tube bundle located inside, equipped with a fin and an additional system of perforated pipes, the ends of which have openings. Irrigation water is pumped into the irrigation system from a sump. The tube bundle is blown by air drawn in by a fan through the windows.

The air coming from the window is mixed with a fresh portion of it, sucked through the holes of the perforated pipe system, while the air saturation with moisture is kept at a low level throughout the passage through the apparatus.

A system of perforated pipes with open ends for the passage of fresh saturated air allows you to slightly increase the intensity of heat transfer.

The disadvantage of this cooler is the low heat transfer rate associated with the saturation of the air washing the annulus.

The closest prototype should include an evaporative condenser [3].

This unit combines a conventional condenser and a device for reverse water cooling.

A tubular coil is mounted in a metal casing, in which the refrigerant is condensed, a tubular manifold with nozzles spraying water, a fan, a receiver for the refrigerant coming from the tubular coil and a chipper to prevent the entrainment of water droplets with air.

The condenser is equipped with a pump that pumps water from the sump to the nozzles for irrigation of the coil.

The disadvantage of this evaporative condenser is its relatively low efficiency, since its heat transfer coefficient does not exceed 350-500 kcal / m ² · hour · ° C.

Significant problems in the operation of this equipment cause deposits on the heat exchange surfaces of calcium carbonate salts in the form of scale in combination with products of biological origin, corrosion and dust from the air. Condenser contamination leads to a decrease in the cooling ability of the heat exchange surface due to an increase in aerodynamic resistance to air passage, respectively, to a decrease in its flow rate.

Capacitors with a small finning pitch and, accordingly, with small channels for the passage of water and air are most susceptible to salt deposits and pollution.

The objective of the invention is a sharp increase in heat removal from the surface of the pipes, inside which circulates the cooled medium, reducing water consumption, reducing the duration of the process and preventing pollution of the evaporator.

The problem is solved due to the fact that the evaporative condenser contains a metal casing with a tubular bundle placed in it, finned plates, nozzles, and a fan. According to the invention, after the nozzles, a high-voltage electrode is installed isolated from the housing, charged with a plus sign and the other end mounted on a tubular bundle with a minus sign. The high-voltage electrode is made in the form of a metal grid on which metal needles are welded to the base of the high-voltage electrode, opposite each nozzle.

In Fig.1 shows an air-vapor condenser, a General view;

figure 2 is a graph of the dependence of the coefficient of heat transfer from the surface of the tubular bundle on the speed of the cooling medium during transverse flow.

The evaporative condenser contains a compressor 1 of the chiller, a discharge pipe 2, a tube bundle 3, nozzles 4, a high voltage electrode 5, a power supply unit 6, a fan 7, a pump 8 for the process water cooling circuit, a metal casing 9. Hot ammonia vapors from compressor 1 with temperature t _TH1 enter the tube bundle 3, where it is cooled to a temperature t _TH2 , and a mixture of steam and liquid enters the linear receiver. In this system, the process water circuit is closed and closed. Using the pump of the cooling circuit of the process water 8, water is supplied through pipes to the nozzles 4, from which atomized particles of water fall into the electrostatic field (ESP).

ESP is created by a high-voltage electrode 5, which is made in the form of a metal mesh insulated from the metal casing. Moreover, opposite each nozzle 4 there are metal needles.

ESP creates repeated droplet crushing, efficient turbulization of the film of water flowing through the pipes, and also ensures the bactericidal purity of the system. Particles of water flow down along the plate ribs, worn on the tube bundle 3, in the form of an irrigated film. A flowing film of water removes heat from the surface of the pipes and transfers part of the heat to the circulating air. As a result, the temperature of the irrigated water at the inlet and outlet of the apparatus is maintained constant.

The air passing through the evaporator only accepts heat from the film of water and its state changes i _B1 to i _B2 .

A feature of a water film formed by a stream of droplets is that the droplets continuously perturb the film, introducing a liquid mass into it. The intensity of the effect of the droplet flow on the film depends on the change in the heat transfer coefficient from the heat exchange surface during evaporative cooling in ESP.

Studies have shown positive results.

Figure 2 presents the results of a theoretical study of the dependences of the heat transfer coefficients α on the air flow rate and various cooling methods. From figure 2 it is seen that the highest values of α reaches during evaporative cooling in the ESP. This is because the ESP intensifies the cooling process by: accelerating the movement of droplets, crushing large droplets into smaller ones and uniformly coating the tube bundle with a cooling medium throughout the entire volume of the apparatus.

Thus, we can conclude that an increase in the droplet velocity due to their “acceleration” in the ESP and the crushing of large droplets into smaller ones leads to an increase in the heat transfer efficiency. This is one of the prerequisites for guiding the ESP between the cooling medium and the heat exchange surface in the air-vapor condenser.

The calculations also showed that the heat transfer coefficient reaches its maximum value at an air speed of V = 1.8 ... 2.2 m / s with a field strength of E = 20-25 kV / m.

Literature:

1. USSR author's certificate No. 792069, cl. F 28 F 5/00, 1979

2. USSR Copyright Certificate No. 937952, cl. F 28 D 5/00, 1982

3. Zaitsev V.P. Refrigeration equipment. - M .: State Publishing House of Trade Literature, 1962. - S.149-150.

Claims (2)

1. Evaporative condenser containing a metal casing with finned plates, nozzles, a fan placed in it in a tubular bundle, characterized in that after the nozzles a high-voltage electrode is charged, charged with a plus sign and the other end mounted on a tubular bundle with a “ minus". 2. The evaporative condenser according to claim 1, characterized in that the high-voltage electrode is made in the form of a metal grid on which metal needles are located, welded to the base of the high-voltage electrode opposite each nozzle.

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