RU2814476C1 - Water cooling method and device for its implementation - Google Patents

Abstract

FIELD: water treatment.

SUBSTANCE: food and chemical industries, refrigeration equipment, agriculture; intended for producing ice water. The method for cooling water involves initial immersing the entire surface of a heat exchanger in it, which is cooled from the inside, followed by spraying the surface of the ice formed on the heat exchanger with cooled water. The method consists of two stages, in the first of which, on the surface of a heat exchanger vertically located in the tank, consisting of at least two pipes coaxially curled in one direction, a layer of ice with a thickness of no more than four pipe diameters is built up, on which it is frozen, preventing the ice from freezing on adjacent turns, and on the second turn off the refrigeration machine and drain the unfrozen water, after which the ice surface on the heat exchanger is irrigated with cooled water in the mode of a stable film separated flow. A device for implementing the water-cooling method contains a refrigeration machine, a water pump, a sprinkler, a water tank and a heat exchanger. At the bottom of the tank there is a mesh catcher for ice fragments.

EFFECT: increase in specific heat removal by ensuring a stable film separated flow of water and reducing energy costs for its cooling.

3 cl, 2 dwg

Description

The invention relates to the food and chemical industries, refrigeration equipment, agriculture and is intended for producing ice water.

It is known that in enterprises whose work involves the operation of refrigeration units with technological conditions close to 0°C and characterized by uneven heat load, it is very effective to use cold accumulation. Cold can be accumulated during periods of low thermal loads and used during operation and when it is necessary to relieve peak loads on the refrigeration unit.

There is a known method for cooling milk, in which ice is built up on evaporator panels located in the battery tank (see AS No. 1537989). The disadvantage of this method is the absence of separated flow of the cooled liquid and, as a result, low heat removal.

There is a known method for cooling a liquid and a device for its implementation (see RF patent No. 2043711). The method involves supplying liquid to a container and placing it in the most heated layer of a heat exchanger. The disadvantage of this method is the limited scope of application for cooled liquids with different specific densities, high energy consumption, as well as technological complexity.

There is a known method for cooling milk and a device for its implementation (see RF patent No. 1794235).

The disadvantages of this device include: high energy costs for cooling, amounting to at least 25 kWh of electricity per ton of chilled milk; the complexity of the installation containing two irrigation-type heat exchangers, the first for cooling milk with “ice” water, the second for accumulating ice, which leads to additional capital costs for the heat exchange surface compared, for example, with milk cooling tanks. The use of a water-ice accumulator is impossible without a temperature difference, which entails thermodynamic losses, thereby reducing the efficiency of the refrigeration machine cycle. Heat exchange through the wall between water (intermediate coolant) and, for example, milk requires an appropriate temperature difference and, therefore, additional work of the thermodynamic cycle.

The known method RU2402899C2 adopted as a prototype. The method involves spraying cooled liquid onto the surface of the heat exchanger. The liquid is supplied to the outer surface of the heat exchanger, which is cooled from the inside by a refrigerant from a series of refrigerants. The disadvantages of this device include the inability to accumulate cold and, accordingly, unnecessary energy costs for cooling the liquid.

The purpose of the present invention is to intensify the method for producing ice water and stabilizing its temperature at the outlet of the apparatus at food industry enterprises.

The goal is achieved due to the fact that this invention combines the advantages of film flow and phase transition (melting) with periodic destruction of the laminar sublayer at the phase boundary between the cooled liquid and ice. Periodic destruction of the laminar sublayer is most clearly manifested in horizontally separated flow of water with the fall of the jet to the next level below the pipes with ice. Film flow is a type of so-called passive turbulization of the flow, therefore, other things being equal, it is characterized by a significantly higher heat transfer intensity compared to processes occurring in the volume of liquid (water) or in completely filled channels. This is due to the fact that a vertically flowing film is an energetically active medium, due to gravitational forces and is always covered with waves: sinusoidal, turning into three-dimensional random motion, and then into shock waves, covered with a network of secondary small capillary waves, which further intensify the processes in the film layer. In this case, the thickness (diameter) of the frozen ice on the coils of the heat exchanger should be no more than 4 diameters of the tube used. To prevent ice from sticking together, the device is equipped with a special device to turn off the refrigeration machine when the specified diameter of ice on the tubes is reached.

The technical challenge is to increase the specific heat removal by ensuring a stable film-separation flow of water and reducing energy costs for its cooling.

This is achieved by the fact that cooled water is supplied directly to the outer surface after a certain layer of ice has been formed on the heat exchanger, while the ratio of the maximum (external) diameter of the coil of the coaxial twisted heat exchanger to the total height of the coaxial heat exchanger is no more than 1 to 3. The given shape is determined by observing a certain pitch L _w =2r _ice +2r _tube +l _{gap l-l} and the angle of inclination between the turns of pipes, amounting to: depending on the diameter of the spiral, taking into account maintaining the compactness of the heat exchanger. All heat exchanger spirals are wound in one direction.

The device has the form of a vertically located coaxial heat exchanger in a tank container, the minimum diameter of the tank is selected based on:d _{turn max} +r _tubes + r _ice + l _{clearance s-l} .

Designing a device in violation of these dependencies can lead to either freezing of the ice into a single mass, or the formation of gaps large enough for the free passage of cooled water past the ice, which will lead to an increase in the outlet water temperature. Both of these options will lead to inefficient operation of the heat exchanger.

The outlet temperature of the water cooled during operation of the ice accumulator is 0 - 4 °C, which is in demand, for example, in the dairy industry and allows milk to be cooled to the lowest possible temperature without the risk of freezing. This method of producing ice water is implemented in an ice accumulator with film separated flow.

Figure 1 shows a schematic diagram of the device.

The device contains a tank 1, a coaxial heat exchanger 2, a refrigeration machine 3, a drain valve 4, a sprinkler 5, liquid flow limiters 6, special mesh reflectors 7, and support posts 8.

Figure 2 shows a drain valve with a mesh insert to catch ice fragments

The device works as follows.

During periods of reduced heat load (for example, at night when energy consumption tariffs in production are reduced), tank 1 with heat exchanger 2 is filled completely with water (i.e. until the liquid level exceeds the uppermost turn by a height equal to calculated thickness of ice formed on the heat exchanger tube upon completion of the freezing process). The refrigeration machine 3 connected to the heat exchanger is turned on, the refrigeration machine operates until the required thickness of the ice layer on the heat exchanger tubes is reached.

After turning off the refrigeration machine, water with a temperature of 0 to 1.5 degrees Celsius from the container is immediately used as a ready-made volume of ice water when the device starts operating. After using the ice water remaining when the refrigeration machine is stopped, cooled water is supplied from the sprinkler 5, and through the use of a water flow-directing limiter 6, its uniform distribution is ensured along the entire perimeter (diameter) of the heat exchange surface. The drain valve for supplying cooled water to the consumer 4 - Fig. 2 at the bottom of the tank is equipped with a mesh that catches breaking ice from the pipes in operating mode, which allows you to use all the accumulated ice. To prevent the cooled liquid from draining without contact with the ice surface, the device is equipped with special mesh reflectors 7, installed around the heat exchanger on support posts 8, and returning the cooled water to the ice surface.

Claims (3)

1. A method of cooling water, including the initial immersion of the entire surface of a heat exchanger in it, which is cooled from the inside, followed by irrigation of the surface of the ice formed on the heat exchanger with cooled water, characterized in that the method consists of two stages, in the first of which on the surface of a vertically located in the tank a heat exchanger consisting of at least two pipes coaxially curled in one direction, a layer of ice with a thickness of no more than four diameters of the pipe on which it is frozen is built up, preventing ice from freezing on adjacent turns, and on the second turn the refrigeration machine is turned off and the unfrozen water is drained, after which the ice surface is irrigated on a heat exchanger with cooled water in a stable film separated flow mode. 2. A device for implementing the water cooling method according to claim 1, containing a refrigeration machine, a water pump, a sprinkler, a water tank and a heat exchanger, wherein the pitch angle of the turns of at least two heat exchanger pipes coaxially curled in one direction is determined by the ratio and in the lower part of the tank there is a mesh catcher for ice fragments that break off during the cooling process of the water. 3. The device according to claim 2, in which the optimal dimensions of the tank are selected based on d _{turn max} + r _tube + r _ice + 1 _{gap s-l} .