What is a passive air-conditioning, operating principles

With the arrival of hot summer inevitably arises the problem of air conditioning. Though not in all regions, but still in very many hot stale air - a very real problem that may bring trouble at home or at the office. To solve it, you can buy a conventional air conditioner, which is also called split-system. But they are quite expensive in itself, and also consume a lot of electricity, which affects the cost. It is not always the use of conventional air conditioners feasible and justified, sometimes much more profitable to install air conditioning in the house passive cooling. In this article, we will reveal what constitutes passive air conditioning and what is the principle of their work.

  1. What is a passive air conditioning
    • Geothermal circuit and the well
    • Fancoils
    • Circulation pump
  2. The operating principle of passive air-conditioning
  3. Other options for passive cooling

What is a passive air conditioning

Air conditioning can be carried out in various ways. And we've learned that air conditioning is such an elongated piece, which hang from the ceiling. From it blows cool air, and the outside walls of the house is a box with a fan and a dripping condensate. So passive air conditioners are arranged quite differently.

The most simple and relatively cheap option arrangement of passive air conditioner consists of the elements:

  • Geothermal loop (hole in the ground).
  • Air cond.
  • Circulation pump.
  • Heat transfer fluid in the circuit.

Such a system is capable of lowering the temperature in the room at 4 - 6 ° C and has a capacity of 1 to 2 kW. The figure of 2 kW or more commonly stated by the manufacturer of systems, but in fact a lot depends on the region, the soil structure and the overall temperature in the region, both air and ground. But on 1 kW of power can be calculated easily.

If the power of the system is insufficient, the heat pump is added to it. It should be a unit and pays dearly for a long time. But if one is to create a heating and cooling system based on geothermal heat pump circuit, it turns out very favorably. Use the heat pump to cool the air in the summer just is not profitable. Please note that it is not profitable, not because the cost of electricity and other high cost, and because the original cost of the heat pump is very high.

So, let's look at the elements of passive air conditioner more.

Geothermal circuit and the well

Geothermal circuit and the well

Geothermal circuit presents a vertical well bore in the earth. The deeper the well, the more heat can be extracted from it. For example, a well depth of 40 m can give a 2 kW power, practically as a split system.

Is lowered into the wellbore collector of U-shaped plastic tubing. You can use other pipe, but plastic are the most optimal. They are cheap, and the performance is good enough to collector served 50 years.

The tube is filled with fluid which circulates in the system. It is also called the refrigerant. In conventional heat pumps use a special ice-free refrigerant, but in a passive air conditioner, you can use plain water. So less operating costs and replenishment of accidental loss.

Important! Note that if the heat pump is to be used, as a coolant must circulate a special fluid - the refrigerant.

Usually it is the high cost of drilling stops the owners of suburban housing before installing the passive air conditioning. But due to the fact that a hole in the ground are requirements are much less stringent than those for the water well, for example. Therefore, even for drilling a deep well 40 m can be used small drills as BUR-50. Especially if the ground 3 - 4 degrees of drillability, which include clay, sand and limestone.

The costs of drilling of 40 m depth of the well does not exceed 500 USD The cost of plastic pipes and couplings - about 100 USD

The well in the ground - not the only option for a passive collector conditioner. It is also possible to omit the water reservoir, the temperature of which is sufficient to cool the circulating coolant is at least 3 - 5 ° C. For example, the collector may be lowered into the well with cold water or in a mountain stream.



The next element of the system that provides a passive cooling are fancoils. These units are called "polukonditsionery".
Fan coil unit consists of a heat exchanger, the fan, and filter control unit.

Inside the heat exchanger circulates the refrigerant / coolant. The fan blows air to the heat exchanger where it cools and blows cold air back. The filter cleans the air. A control unit is needed in order to adjust the air temperature in the room.

The operating principle of the fan coil

If vdatsya bit in detail, the fan distributes the air uniformly over the entire area of ​​the heat exchanger, so that it is uniformly cooled or warmed (if the fan coil used for heating).

The fan motor is of two types:

  • Tangential - used for low-power fan coil units in small spaces;
  • Centrifugal - used in Fancoil medium and high power. Typically, these are installed in enterprises or other large spaces.

Thus, the fan blows air and delivers it through a heat exchanger. Self heat exchanger and pipes suitable to him, often copper. The pipes inside the heat exchanger receives refrigerant or heat transfer fluid. It may be water, cold or hot, or ethylene glycol.

Fan coils can control air temperature in the room in two ways: either by regulating the volume of supply air, or the volume of water in the heat exchanger. The water flow can be controlled by a special valve, which changes the cross-sectional diameter tube. Thus, changing the flow of water entering the heat exchanger.

Important! The ability to adjust the volume of incoming water - water systems, the fundamental difference of freon.

Air flow rate can be controlled by changing the fan speed. It will pump air into a smaller or greater extent.

Fan coils installed in all rooms where air conditioning: in hallways, bedrooms, hallways, kitchen and other rooms. fan coil price starts from 200 USD They look superficially the same as conventional air conditioners with capacity of 2 kW, with a remote control and adjustment of the cooling rate.

Circulation pump

The circulation pump is needed in the system to cause the fluid to circulate on the loop system. Water passes through the geothermal loop is cooled there and goes straight into the fan coil heat exchanger.

Electricity consumption is very small circulating pump, and the pump itself costs about $ 100 Installation works of all passive cooling system will cost about $ 100 Total passive air conditioning will cost $ 600, about the same as a conventional split system.

Besides represented conditioner passive elements in a heat pump can be included. If the power of the basic elements is not sufficient, the refrigerant is further cooled in the compressor and only then enters the fan coil heat exchanger.

The operating principle of passive air-conditioning

The operating principle of passive air-conditioning

Let's take a closer look at the principle of the passive air conditioner and how the work of ventilation and air conditioning in rooms.

Thus, we assume that the system circulates plain water.

Passing through the precoat heat exchanger which we have named just above loop geothermal water cools down to a temperature which is clearly below the ambient temperature at the surface. For example, the window +30 ° C. The water passes through the circuit and is suitable to a heat exchanger with a fan coil temperature +19,5 ° C.

The principle of operation of passive cooling

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Cooling air passing through the fan coil heat exchanger, the water is heated and exits heat exchanger with a temperature +21,2 ° C. It would seem that the difference is small. But let's dig deeper.

Cooling hour is 715 watts. But electricity costs much less: fan coil consumes only 70 watts, and the circulation pump 120 watts. Incidentally, the pump may be a few, while their consumption must be summed.

After the water has given her the cold air, it returns to the subterranean reservoir, where it is cooled again, and so the cycle repeats.

Important! The higher the temperature overboard, the higher the efficiency of the passive air conditioner. When the temperature is low, for example, +20 ° C, the effectiveness of passive cooling is practically zero, because a small temperature difference between water and air.

If the system will not circulate water and ethylene glycol, and in the system of the heat pump is added to the compressor, the air conditioning efficiency will be much higher, but costs too.

The basic problem with passive conditioners dirt collector is a flow resistance, because of which have to increase capacity of the circulation pumps.

The simplest solution to this problem - the use of the least viscous fluid. If this water is then distilled, diluted softener reduces the viscosity.

In addition, you can take a number of other measures:

  • To reduce the steepness of the turns in the pipe system. To this end, the rotary elements must be replaced by oblique with an obtuse angle.
  • You should also reduce the number of joints, which reduces the diameter of the pipeline section. Better use of the coupling without changing the diameter.
  • Minimize the number of shut-off valves - the valve.
  • Fan coils can be used, in which the heat exchanger tube of larger diameter.

In the table below you can see the most problematic sections of the pipeline. Note that the smaller the coefficient given in the last column, the lower the flow resistance in the system.

Table 1. The resistance coefficient of the pipeline elements.

Table 1. The resistance coefficient of the pipeline elements.

Eliminating the elements of the system with the highest resistance, can significantly increase the effectiveness of the passive air conditioner with a soil collector.

Another important point in the passive air conditioning - ventilation. For normal operation of fan coil units should be fresh air. And here it should be noted that the fan coils can be used when the window is open, in contrast to the type of air conditioners split system.

Besides air flow through the window, it is possible to implement air flow via the central air conditioner which is installed on the roof or loft building.

Other options for passive cooling

Passive cooling is not always realized with the help of fan coils. For example, in areas where motion is undesirable excess air masses or noise from the fan coil fan can use so-called cold walls, ceilings or floors colder.

cold floors system is almost the same as the system "warm floor". Under flooring tested pipe which circulates chilled liquid. Thus, the fluid cools the floor surface.

cold wall

Noninferiority have cold walls and ceilings. Cooling ceiling air descends on the laws of physics by creating the optimum room temperature.

Called the floor, ceiling and walls of cold can be only conditionally. Typically, the temperature of these surfaces is not less than +15 - +16 ° C, so that formation of dew.

In conclusion, I would like to reiterate the benefits of using passive air conditioning. The power consumption of 2 kW cooling installation does not exceed 80 - 100 watts. A conventional air conditioner 2 kW consumes less than 800 watts. The benefit is obvious, passive air conditioning consumes 10 times less, respectively, it pays for itself in a few seasons.

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