Method and device for cooling circulating air

ES 2 264 019 T3

DESCRIPTION

Procedure and device for cooling circulating air.

The invention concerns a method and a device for cooling circulating air by means of heat exchange with adiabatically cooled process air.

The invention belongs to the sector of so-called indirect adiabatic cooling, since the water necessary for adiabatic cooling is not introduced into the circulating air, but into the process air, which preferably consists of outside air. The adiabatically cooled process air acts as an enthalpy dissipator in the exchange of heat with the circulating air and lowers its temperature.

The cooling capacity of such systems depends on the starting temperature and humidity of the process air. When, for example, this temperature is relatively high, the cooling capacity is not sufficient to effectively cool the circulating air. Thus, up to now, it has been forced to use an additional compression or absorption refrigeration installation; see, for example, DE41 35 431 A1.

Such refrigeration installations increase the technical cost of the device. They consume highly valuable energy in the form of electrical current or fossil fuels and, in addition, they work with refrigerating agents that pollute the environment. Legal provisions are increasingly necessary to regulate the consumption of highly valuable energy and the use of environmentally polluting materials.

The invention is based on the problem of increasing the efficiency of indirect adiabatic cooling of circulating air with simple means.

In order to solve this problem, the method mentioned at the beginning is characterized according to the invention in that the cooled process air, after its heat exchange with the circulating air, absorbs heat from the non-cooled process air.

After its heat exchange with the circulating air, the cooled process air has a temperature that is below the temperature of the uncooled process air. Therefore, it can absorb heat from the uncooled process air, thereby lowering its temperature. Consequently, adiabatic cooling acts on a process air whose temperature has already decreased. This produces cooling of the circulating air, in particular with the result that - in applications where sensible cooling of the circulating air is sufficient - additional compression or absorption refrigeration installations can be dispensed with. The technical cost of equipment necessary for this is small. Apart from investment costs, operating costs also decrease, as less energy and water are consumed.

Likewise, it should be noted that no authorization procedure is necessary for the operation of the cooling installation. Maintenance is simplified as no cold specialist has to be added. Any pollution of the environment attributable to the use of refrigerating agents is also eliminated.

Adiabatic cooling of the process air can take place before this process air enters into heat exchange with the circulating air. We can then speak of a two-stage evaporation. A single stage evaporation may be more advantageous, in which adiabatic cooling of the process air takes place during the heat exchange with the circulating air. In contrast to two-stage evaporation, the heat exchange surfaces are moistened here with the injected water.

Depending on the operating state, the water temperature may vary during single-stage adiabatic cooling. It has surprisingly been found that significant repercussions on the conduct of the process result from this. When the temperature of the water decreases, it is advantageous to conduct the circulating air and the process air in an isocurrent circuit during their heat exchange. Otherwise, the countercurrent circuit is more favorable. Therefore, in refinements of the invention it is proposed that the circulating air and the process air are conducted during their heat exchange in isocurrent, countercurrent or cross current or in isocurrent cross or counter crosscurrent.

The cooling capacity can preferably be regulated by varying the circulating air / process air mass flow ratios and / or by varying the amount of water introduced into the process air.

The cooled process air is preferably sucked in after it has absorbed heat from the uncooled process air.

The device to solve the problem posed presents a first heat exchange equipment that can be loaded with the circulating air and with process air, as well as a humidification equipment to introduce water into the process air, and is characterized according to the invention by a second heat exchange equipment to effect a heat exchange between the air of the uncooled process before its entry into the first heat exchange equipment and the process air cooled after its exit from the first heat exchange equipment. Therefore, the process air first passes through the second heat exchange equipment and then the first heat exchange equipment, after which it is evacuated through the second heat exchange equipment. In the second heat exchange device, the cooled process air absorbs heat from the uncooled process air and thus lowers its temperature.

Advantageously, the second heat exchange device can be bypassed at least on the inlet side of the uncooled process air by means of a bypass, specifically in the event that the temperature of the uncooled process air makes pre-cooling of the same in the second heat exchange equipment. From this point of view, the humidification equipment can also be advantageously switched off. Finally, a preferred possibility is to work with a so-called free cooling, in which the outside air is used for direct cooling of the room.

The humidification equipment can be constructed as a scrubber, a contact humidifier, a high pressure humidifier or the like. It can be found between the first and the second heat exchange equipment. As mentioned, this class of dis2

ES 2 264 019 T3 position can be designated as two-stage evaporation. In certain circumstances, single stage evaporation is more advantageous, in which the humidification equipment is integrated into the first heat exchange equipment . Therefore, the water is injected directly into the first heat exchange equipment and this water moistens its heat exchange surfaces.

Preferably, the first heat exchange equipment can be operated here in countercurrent, isocurrent or crosscurrent, depending on whether the temperature of the water is increased or decreased during adiabatic cooling.

In an important further development of the invention, it is proposed that the first heat exchange device has at least two cross-current heat exchangers, these can also preferably be operated in counter-cross-current or iso-cross-current.

Advantageously, the process air is sucked in by a blower which is arranged in the path of the cooled process air downstream of the second heat exchange equipment. Therefore, the blower draws the process air through the device. The arrangement has been chosen in this case so that the heating of the process air forcibly generated by the blower does not impair the cooling capacity.

In the following, the invention is explained in more detail with reference to a preferred embodiment in conjunction with the attached drawing. The drawing shows in:

FIG. 1 a device according to the invention in schematic representation; Y

Figure 2, the state variations of the circulating air and the process air in the h, x diagram.

According to FIG. 1, a first heat exchange device 1 is provided which contains two cross-current heat exchangers 2 and 3. The first heat exchange equipment 1 is requested with circulating air 4, specifically this air first passes through the cross-current heat exchanger 2 and then the cross-current heat exchanger 3. A blower 5 provides the transport of the circulating air 4.

The first heat exchange equipment 1 is also ordered with process air 6, which in the present case consists of outside air. The process air 6 also passes through the cross-flow heat exchanger 2 first and then the cross-flow heat exchanger 3. Therefore, the first heat exchange equipment 1 works in a cross isocurrent circuit, which is advantageous because the operating state of the device leads to a cooling of the water injected into the first heat exchange equipment 1.

The first heat exchange equipment 1 is provided for this with a humidification equipment 7 which sprays the water into the process air 6 and thus produces its adiabatic cooling. The water collects in a sump 8 and is fed by a pump 9 to the humidification equipment 7. The sump 8 is provided with a water inlet 10 and a water outlet

11.

Before entering the first heat exchange equipment 1 and after leaving the latter, the process air 6 passes through a second heat exchange equipment 12, specifically under the action of a blower 13 which, referred to the air from The cooled process is arranged downstream of the second heat exchange equipment 12. The heat generated by the blower 13 cannot impair the cooling capacity. Since the temperature of the cooled process air 6 after its exit from the first heat exchange equipment 1 is lower than the temperature of the process air 6 before its entry into the second heat exchange equipment 12, it can be performed in the latter a heat exchange between the two streams of the process air 6, specifically with the result that the process air 6 already endowed with a reduced temperature is subjected to adiabatic cooling. The consequence is a corresponding increase in the cooling capacity.

Figure 2 shows in diagram h, x an example of a single-stage adiabatic cooling such as that which can be carried out with the device according to figure 1, reproducing a line at the drop in temperature of the circulating air 4 in the first heat exchange equipment 1. A line b shows the drop in temperature experienced by the process air 6 in the second heat exchange equipment 12. A line c reproduces the decrease in temperature of the process air 6 due to the effect of adiabatic cooling in the first heat exchange equipment 1, and a line d shows the increase in temperature of the process air 6 in the second heat exchange equipment 12.

Within the framework of the invention there are certainly possibilities for variation. Thus, the direction of transport of the blower 5 can be reversed. The first heat exchange device 1 then works in a cross-countercurrent circuit. This working mode will be chosen when the water temperature between the inlet and outlet of the process air does not drop. Likewise, there is the possibility of decoupling the humidification equipment from the first heat exchange equipment and let it work between the two heat exchange equipment. However, the integration of the humidification equipment in the first heat exchange equipment is especially advantageous. The first heat exchange equipment can be constructed with a single stage and likewise the second heat exchange equipment can have a multi-stage structure. Furthermore, it is possible to bypass the second heat exchange device with a bypass, whereby the lines b and d are suppressed in the diagram according to figure 2. When, in addition, the humidification device 7 is switched off, which it is also possible, then line c is also deleted. The cooling effect then results solely from the temperature difference between the circulating air and the process air. Finally, the first heat exchange device can also be uncoupled. The process air is then blown directly into the room to be cooled.