How to save money on air conditioning with a heat exchanger

Recommendation points

• Collector
• Channel
• Radiator or plate
• Rotary
• Peltier element recuperator
• Liquid
• DIY recuperator
• Option one. Lamellar
• Option two. Tubular

How to reduce heating costs if the house is equipped with supply and exhaust ventilation? In this article we will talk about devices that allow you to heat fresh cold air due to the temperature of the exhaust. It will be about air heat exchangers – recuperators.

The idea of ​​heat recovery has been popular for a long time. Global warming and the high cost of energy makes people think about saving even those whose energy costs are negligible compared to industrial ones. So, let’s “hit” the first law of thermodynamics on heating costs.

The idea underlying the operation of all recuperators is simple, like everything ingenious – the transfer of heat energy through a denser medium (metal or water). This process occurs naturally, due to the work of the laws of physics, therefore heat transfer is carried out without additional costs. All recuperators are divided according to two criteria: principle of operation (design) and method of installation. Consider the options for recuperators by installation method.

Collector

The supply and exhaust are collected in common channels, and a collector with a heat exchanger is installed at a certain place. Large collectors serving many rooms are installed on the roof (rooftop recuperators). It is one of the main units of the supply and exhaust ventilation system. Part of the channel system.

Advantages:

1. Allows you to choose a convenient location for the unit – in the attic, under the ceiling or in the basement.
2. Performance (and hence the price) is calculated together with the ventilation system, which allows you to choose the best option and not overpay.
3. Does not require additional holes or openings for mounting the device itself.
4. The recuperator units can be replaced individually.

Disadvantages:

1. When installed in cold rooms, additional thermal insulation is required (insulated box).
2. Requires special skills and knowledge, in particular when calculating and installing.
3. Has tangible linear dimensions (from 600x600x200 mm).

Channel

The recuperator is a pipe structure that is installed in a channel laid in the wall. Some models have a function of “heating”.

Advantages:

1. Fully self-contained device requiring only electrical connection.
2. Ease of installation.
3. Simplicity of calculations (selection of power by the volume of the room).
4. Compactness – does not require additional space (located inside the wall).

Disadvantages:

1. Only serviced in workshops.
2. Channel laying in the wall (diameter from 150 mm).
3. Serves only one room.
4. Relatively high noise level.

The common factor for both types is that they can be used with different types of heat exchangers. They also provide for the optional installation of various filters..

A more important feature of a recuperator is the type of heat exchanger that is installed in it. This parameter often becomes decisive when choosing a unit. Time should be taken into this matter as performance and features can vary significantly. Consider the options for the heat exchanger device. In evaluating the pros and cons, we consider that each system requires air supply fans. Also, a common symptom will be the formation of condensation (to varying degrees).

Radiator or plate

The simplest, but at the same time effective form. Air of different temperatures passes through a channel separated by a conductive medium – a metal (plastic, paper) plate or tube surface. Temperature is transferred through the denser medium of the plate material.

Advantages:

1. Has no moving parts. Mechanical wear-free design.
2. Does not consume energy.
3. Possibility of handicraft assembly of an effective device from scrap materials (from market “breakdowns”).

Disadvantages:

1. Relatively low efficiency: 40-65% *.
2. Condensation of moisture on the ribs, and, as a result, icing (requires a bypass device for periodic “defrosting”).

* – compared to rotary. Efficiency of 50-60% is considered the norm for air recovery.

The price fluctuates a lot depending on the performance. So, to meet the needs of a country house with an area of ​​60 sq. m the price of the device will start at 15,000 rubles and more (depending on the volume of the premises). Recuperators with industrial performance will cost from 25,000 rubles.

Rotary

It is a constantly rotating drum filled with honeycombs (through channels) with a diameter of 2–4 mm. The ventilation ducts are fed into equal parts of the drum, but do not intersect. The air flow constantly blows the ribs of the honeycomb (tubules) and transfers them the temperature, which is transferred by rotation to another compartment.

Advantages:

1. Highest efficiency – up to 85%.
2. Control of electronics for energy consumption depending on temperature difference.
3. Allows to regulate heat exchange (drum rotation speed).
4. Carries some moisture (does not dry the air).
5. Minimal condensation. No winter icing (due to electronic control).

Disadvantages:

1. Simple design requires sophisticated control automation.
2. Requires constant power supply.
3. Requires a separate seat.
4. Self-assembly and maintenance requires professional skills.

A complex and high-performance system will cost from 60,000 rubles.

Peltier element recuperator

A thermoelectric module acts as a heat exchanger.

Advantages:

1. Elementary (amateur) construction.
2. Low power consumption.
3. Recuperator elements availability.
4. Doesn’t require special skills.

Disadvantages:

1. Low efficiency – 20%.
2. Low productivity.
3. Doesn’t work without electricity.
4. Extremely narrow scope.

There are no such factory-made devices, and they are unlikely to withstand competition with traditional proven devices. The price of such a unit will consist of the cost of purchasing its parts – about 1000 rubles.

Liquid

Has a radiator with a liquid agent (water, antifreeze). Since the efficiency of such a recuperator is almost equal to that of a plate recuperator, and the design is incomparably more complicated (and therefore more expensive), we will not describe it in detail (it does not participate in the rating).

DIY recuperator

In this part of the article, we will analyze prototypes of homemade radiator heat exchangers. This design is accepted by us as the simplest and most effective..

Option one. Lamellar

Method 1.Such a radiator can be made from any profiled material – thermal conductivity is not critical, the main thing is that it is thin. These can be plates of galvanized profiled sheet or any similar material. The more often there are bends on the profile (air vents), the more efficient the radiator will be. Cut out to one size (300×300 mm) and glue it with a neutral sealant, alternating the direction of the channels, until the structure reaches the shape of a cube.

Method 2.Metal plates. If there is a flat sheet metal 1–2 mm thick (preferably aluminum), then the radiator can be made from it. We cut out straight rectangles of a given size (in our case, 300×300 mm). We cut strips with a width of 20 mm and a length along the plate (300 mm). We glue the strips with sealant on the plates, two at the edges and one in the center. We alternate the direction of the plates so that it turns out like this: one “floor” is viewed along, neighboring across.

The radiator is ready. Further, you will only need 4 socket adapters for the pipe diameter (usually 150 mm), which can also be made independently from galvanized steel. Then the whole structure is installed in a thermobox – an insulated box with a condensate channel. On the sides of the box there should be holes through which we will include the recuperator in the ventilation system.

Attention! The main nuance of the installation is that the radiator cube should be tilted relative to all channels. This is necessary in order for the condensate to be removed by gravity..

Option two. Tubular

We need flat metal tubes with a diameter of 10 mm – about 30 linear meters. m, a stainless steel plate (aluminum, duralumin) 300x150x1-2 mm, a sewer pipe with a diameter of 150 mm and a length of 1.5 m, two tees, adhesive sealant for metal (neutral).

Attention! The use of an acid based sealant can lead to corrosion in all cases.

The main difficulty of this option is to cut two plates exactly and drill mirror-like holes in them. Hole arrangement principle: the hole area is 40% of the entire plate area. In short, if the outer diameter of the tubes is 12-13 mm, there will be 20 holes. They must be mirrored on both plates.

Advice.It is better to entrust this part of the work (plates) to a professional.

We assemble the recuperator body – we put on a pipe for 1.5 m on a tee on both sides. We carefully measure the size of the tubes so that after installation it does not take the place of subsequent elements. We carefully cut the tubes. We fasten the tubes into plates (they should stand at the ends of the tubes) with glue-sealant. After drying, we mount the structure in the body (pipe). Recuperator ready.

Install in the system, maintaining the slope for condensate drain.

The cost of the above homemade units is difficult to calculate, given the local capabilities of the master (all parts can be found in the garage). Therefore, we will take a notional value equal to 1000 rubles..

This is how, practically free of charge, you can organize air heating for air heating and other purposes. Calling on the forces of nature, the laws of physics and our own ingenuity, we move towards harmony with the world around us. How to calculate and select equipment for a supply and exhaust system with a recuperator, we will tell you in the next article..