RU2607916C1 - Heat exchanger - Google Patents

Abstract

FIELD: heat engineering.

SUBSTANCE: recuperative heat exchanger, in which one of heat carriers, before entering into heat exchanger, passes through mixer, in which is mixed with same heat carrier, but already passed through heat exchanger, pressurized by compressor. Heat exchanger, being recuperative, by efficiency (heat carrier temperature equalization capacity) corresponds to mixing heat exchanger.

EFFECT: technical result is increase in heat exchanger efficiency.

3 cl, 3 dwg

Description

The invention relates to heat engineering.

Recuperative, regenerative, and mixing heat exchangers are known (BES, Volume 25, Third Edition, Moscow: Soviet Encyclopedia, 1976. P. 455).

Recuperative heat exchangers are devices in which heat carriers with different temperatures are separated by a solid wall. The disadvantage of recuperative heat exchangers is significant thermal resistance, which prevents the transfer of heat from one coolant to another.

Mixing heat exchangers are devices in which heat transfer occurs upon direct contact of heat carriers, which ensures the maximum possible transfer of heat from one heat carrier to another. The disadvantage of mixing heat exchangers is that the physical properties of the coolants change when mixed.

The aim of the invention is to provide the maximum possible transfer of heat from one coolant to another (as in mixing heat exchangers) while maintaining the physical properties of the coolants (as in regenerative heat exchangers).

A heat exchanger is known in which heat carriers with different temperatures are separated by a solid wall, and one of the heat carriers, before entering the heat exchanger, passes through a mixer in which it is mixed with the same heat carrier passing through the heat exchanger and pumped (CN 103415538 A, IPC C08F 2/01, C08F 2/18, publ. 11/27/2013).

This goal is achieved in that in a heat exchanger in which heat carriers with different temperatures are separated by a solid wall, one of the heat carriers, before entering the heat exchanger, passes through a mixer in which it is mixed with the same heat carrier passing through the heat exchanger. At the same time, the flow rate of the coolant coming from the heat exchanger to the mixer is more than 90 percent of the flow rate of the coolant coming from the mixer to the heat exchanger. A compressor is used to supply the coolant from the heat exchanger to the mixer. As the heat carrier gas or liquid is used.

The essence of the invention lies in the fact that the temperature change of one of the coolants and heat transfer between the coolants are carried out separately. The change in temperature of the heat carrier is carried out in a mixing heat exchanger (mixer), and the heat exchange between the heat carriers is carried out in a recuperative heat exchanger. The heat exchange in the recuperative heat exchanger leads to a change in the temperature of the coolant, which is amplified in the mixing heat exchanger, and so on until a minimal temperature difference is established on the dividing wall of the regenerative heat exchanger. The temperature difference is the smaller, the more coolant from the recuperative heat exchanger returns to the mixing heat exchanger: at 90 percent return of the coolant, the heat transfer efficiency of the regenerative heat exchanger practically does not differ from the heat transfer efficiency of the mixing heat exchanger, and the physical properties of the coolants are preserved.

In FIG. 1 shows a heat exchanger;

in FIG. 2 shows a thermodynamic cycle implemented in a heat exchanger;

in FIG. 3 shows heat exchanger performance characteristics.

The heat exchanger (Fig. 1) consists of a regenerative heat exchanger 1, compressor 2, mixer 3, inlet channel 4.

The heat exchanger is as follows. The coolant (gas) under pressure through the inlet channel 4 enters the mixer 3 and then into the heat exchanger 1. The cooled (heated) heat exchanger 1 partially transfers the heat carrier to the consumer. The remaining part of the coolant enters the compressor 2, from which to the mixer 3. In the mixer 3, the cooled (heated) coolant is mixed with the coolant entering the mixer through channel 4. As a result of mixing, the coolant temperature decreases (rises). The resulting mixture enters the heat exchanger, and the cycle repeats. The change in temperature of the coolant will continue until the alignment of the heat fluxes in the heat exchanger 1 and the mixer 3.

In FIG. 2 shows a thermodynamic cycle implemented in a heat exchanger. The working fluid of the cycle is gas (heat carrier) circulating inside the heat exchanger 1 (the gas temperature inside the heat exchanger is higher than the gas temperature outside the heat exchanger). The gas (process a-b) expands and cools in the heat exchanger (heat q ₂ is removed). The cooled gas is compressed to the initial pressure (process bs). Heat q _{1 is} supplied to the gas at constant pressure (process c-a). The cycle repeats. The amount of supplied and removed heat is equal (q ₁ = q ₂ ), since all the work of gas expansion (process a-b) is converted into heat.

The amount of supplied (removed) heat in the cycle (Fig. 2) depends on the intensity of heat transfer processes and the mass of the working fluid of the cycle.

The intensity of heat transfer processes is characterized by a coefficient of intensity of gas cooling

,

,

where Ta and Tb are the gas temperatures at points a and b of the cycle,

T ₂ - the initial temperature of the external gas (second coolant).

The mass of the working fluid involved in heat transfer is characterized by the coefficient of circulation of the gas (coolant)

,

,

where G ^* is the flow rate of gas from the heat exchanger to the mixer,

G is the flow rate of gas from the mixer to the heat exchanger.

The gas temperatures in the cycle a-b-c are defined as

,

,

,

,

,

,

where T ₁ and T ₂ are the initial temperatures of the internal and external gas (first and second coolants, respectively);

π is the degree of pressure increase in the compressor;

η _s - efficiency in the process of compression;

k is the adiabatic exponent.

In FIG. 3 shows the change in gas temperature at the outlet of the heat exchanger (point b in Fig. 2) depending on the coefficient of gas cooling intensity ϑ and the circulation coefficient δ _c at the initial gas temperatures: T ₁ = 900 K, T ₂ = 300 K and the degree of pressure increase in the compressor π = 1,1. It is seen that for circulation coefficients δ _c > 0.9, the gas temperature at the outlet of the heat exchanger (regardless of the coefficient ϑ) approaches the initial temperature of the external gas T ₂ .

EFFECT: invention makes it possible to approximate the efficiency of a recuperative heat exchanger (the ability to equalize coolant temperatures) to the efficiency of a mixing heat exchanger, which opens up new possibilities for increasing the efficiency power plants, such as aircraft engines, in which the use of such heat exchangers will significantly reduce the air consumption for cooling engines.

Claims (3)

1. A heat exchanger in which heat carriers with different temperatures are separated by a solid wall, and one of the heat carriers, before entering the heat exchanger, passes through a mixer in which it is mixed with the same heat carrier passing through the heat exchanger, pumped by a compressor, characterized in that the flow rate the coolant coming from the heat exchanger to the mixer accounts for more than 90 percent of the flow rate of the coolant coming from the mixer to the heat exchanger. 2. The heat exchanger according to claim 1, characterized in that the coolant is a gas. 3. The heat exchanger according to claim 1, characterized in that the coolant is a liquid.

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