These are thermal pump
split systems. Every air-conditioning unit relocates energy in the form of heat from one place to another. Split means that the system consists of one body outside the building and one or more inside. The most popular are the wall air-conditioners offered in two types:
- Conventional (working at constant compressor power);
- Inverters (with automatic regulation of the compressor power);
Almost all air-conditioners are capable of working in heating and cooling mode. It is a small price difference between them and air-conditioner working in cooling mode only.
Thanks to the regulation of the compressor rotations, the consumable electric power of the inverter air-conditioners is decreased (up to 30 – 40 %). When the room temperature approximates to the intended, they switch to lower power mode operation. Thus they maintain the temperature in optimal limits – with no excess losses of power and at lower noise levels.
The heat power of the air-conditioner is given in BTU (British Thermal Units). 1 BTU is the quantity of heat needed for the temperature increase in one pound of water with one Fahrenheit degree.
To get an idea of the power of an air-conditioner, use the ratio 3.41 BTU = 1 W. Thus for example an air-conditioning of 9 000 BTU has 9000/3.41 = 2640 W power (typically the value is given for cooling mode).
The contemporary air-conditioners have relatively high power efficiency. Every 1 kW consumed electric energy they transform into approximately 4 kW heat energy.
There are two values which manufacturers characterize this efficiency with:
- Coefficient of performance (COP) – in heating mode
- Energy efficiency ratio (EER) – in cooling mode
In catalogues, these parameters have been reported under specific conditions:
- COP is given at temperature + 7°С outside and + 20°С in the room;
- EER is given at + 35 °С outside and + 27°С in the room, at 50% humidity. These conditions often differ from the real ones; therefore it is hard to create an overall preliminary image of the efficiency in practice.
At low winter (-5°С) or high summer (38- 40°С) temperature, the efficiency of the conventional air-conditioners strongly decreases as the lower classes of which even stop working. This problem is better solved in the inverter air-conditioners. They can work in heating mode at negative outside temperature down to – 20°С, something infeasible for a conventional air-conditioner.
It is important to know that:
- An air-conditioner of insufficient power against the room volume, shall operate in non-economic mode despite of its good characteristics (COP and EER). Except that it shall be much more noisy and is likely to be damaged.
- An inverter air-conditioner of higher power would be a better variant in view of power sparing.
- In case the outlet supply air is of temperature lower than the body temperature (< 36.5°С), this air can be sensed as relatively cool and uncomfortable although the room will practically warm up.
- In case of higher humidity in the premise, the air from the air-conditioner can be sensed as cool and uncomfortable although the room will practically warm up.
- In winter, temperatures under minus 20 degrees, the air moisture on the external body shall form frosticles which strongly impair the heat exchange of it. Therefore it is necessary to remove it on a periodical basis. Most of the contemporary air-conditioners have autonomic defrosting mode.
Depending on the fuel, there are various solutions:
Wood and coal furnaces;
Processed oils boilers;
Gas wall boilers;
The ordinary solid fuel furnaces (cut woods or coal brickets) are hard and dirty to service, though quite cheap. The pyrolise boilers ensure better fuel consumption (ashes less than 4-5%) and are capable of continuous burning for 8-12 hours, i.e. they can operate with 1-2 charges a day. They achieve ECE up to 85%. They operate on the principle of dry wood distillation to the emission of generator gas which, mixed with a little air, is supplied for burning. To achieve maximal burning efficiency, the woods must be as less moist as possible (up to 20-30%), to avoid spending its calories for moisture evaporation. Minimal power supply is needed (approximately 40 W) to provide for the process of effective burning.
The boilers and pellet mantelpieces, the efficiency is very high, ECE is up to 94%.
They are comfortably serviced – automatic dosage, supply and burning of the fuel, with self-cleaning option and electronic process control and achievement of the desired temperature. The wooden pellets are pressed wooden waste of small size (diameter 6-10 mm and length 20-30 mm), therefore they allow automatic supply as opposed to the wooden brickets which are approximately ten times larger. They burn effectively, leaving very little ashes (less than 1-2%). They are poured into hoppers and directed to the burning chamber through an auger.
1 tone of pellets is sufficient for heating a volume of 75 m3 per season. To make pellets, fruit stones, wooden bark, wooden chips and other logging wastes are used.
To install and service the boilers being supplied with stored fuel, extra servicing room is needed of area of approximately 4m2 and height 2.50-2.60 m.
The thermal (heat) pump does not produce heat but it utilizes mechanical energy to relocate heat (where you want it – inside or outside the rooms). Thus it operates in two modes – heating or cooling. Тhe refrigerator and air-conditioner are thermal pump aggregates. The thermal pump construction consists of two heat exchangers, a compressor and a refrigerating agent.
The contemporary thermal pumps have high efficiency of conversion of electric energy (from 1 kW consumed electric energy, approximately 4 kW heat energy is sourced at external air temperature 7°С). The system is managed by temperature gauges and optimizes the electric energy cost.
This type of aggregates have supplement heat exchanger that utilizes the heat energy of the air sucked from the room:
In the winter – for heating the cold fresh air coming in the room;
In the summer – for cooling the incoming warm fresh air;
This energy in other cases is lost in atmosphere especially in cooling mode. Through the recuperator, significant energy saving is achieved.
Most of the recuperators utilize the heat from the work of the compressor itself – to supply domestic warm water.
The vapour resistance of a material is a measure of the material’s reluctance to let water vapour pass through. The vapour resistance takes into account the material’s thickness, so can only be quoted for a particular thickness of material. It is usually measured in MNs/g (“MegaNewton seconds per gram”). If the quantity is measured in MNs/gm (notice the small “m” at the end) then it’s actually a vapour resistivity and should be dealt with as explained on the next page. The µ-value (“mu-value”) of a material is also known as its “water vapour resistance factor”. It is a measure of the material’s relative reluctance to let water vapour pass through, and is measured in comparison to the properties of air. The µ-value is a property of the bulk material and needs to be multiplied by the material’s thickness when used in a particular construction. Because the µ-value is a relative quantity, it is just expressed as a number (it has no units). You might see the reluctance of a material to let water vapour pass through expressed as an “equivalent air layer thickness”, which is usually represented as sd. As its name suggests, the equivalent air layer thickness is measured in metres. Like vapour resistance, it can only be quoted for a particular thickness of a material.
You might also see the vapour resistivity of a material quoted. This is similar to the vapour resistance, but is a property of the bulk material and is usually measured in MNs/gm (“MegaNewton seconds per gram-metre”).
An associated unit is the “perm”. This is a measure of permeance, or water vapour transmission. Like vapour resistance, it is a measure associated with a given thickness of material.
Ventilation is a process of air exchange in a building for ensuring of fresh air for the inhabitants. Except for the improvement of the heat insulation, the planning of the building should not neglect the quality of the air in it as well.
There is a variety of reasons that necessitates the ventilation:
The evacuation of the collected carbon dioxide which is harmful;
Тhe reduction of the humidity in the rooms resulting to condense and mould formation;
To provide for fresh air, nothing used to be done in the near past since the joinery works were not well sealed and let through enough air. The utilization of the new PVC and aluminum joinery works “tight” the houses and the air became unhealthy for breathing. Condense moisture and mould appeared in the homes.
To achieve optimal micro-climate in the rooms, it is necessary to ensure more than 25-30m3/h fresh air for a person at relative humidity of 50%-60%. Ventilation is necessary in the mornings for every room for approximately 20-30 minutes, 3-4 more times during the day as well as after cooking, bathing or drying laundry.
The typical ways of room ventilation are:
Through manual opening of windows and doors;
The opening of windows and doors is the most accessible and cheap way of ventilation. But if done frequently, it results in large energy losses. We lose air of optimal temperature and we import air that needs to be warmed or cooled from that moment on. The heat comfort in the room is impaired. Also, we can hardly estimate the ventilation duration.
Through ventilation system with recuperator;
Overall ventilation system (with recuperator) prevents the compromises of the manual ventilation, achieving energy saving. The larger initial investment is a disadvantage.
Through ventilation system with inlet valves;
Ventilation with inlet valves is an intermediate solution option in case of insufficient budget. The heat losses are significantly reduced as opposed to the typical ventilation.
Through micro-ventilation in the window wing;
Ventilation through the upper part of the window (micro-ventilation) is also a solution, but very few companies offer it as an option.
The ventilation through inlet valves is an intermediate solution option for self-regulating ventilation in case of insufficient budget for ventilation system with recuperator.
Self-regulation depends on the humidity level in the rooms. Special humidity sensitive tape reacts to the humidity in the rooms and changes its length. As a consequence of this, the valve is mechanically opened and lets in fresh external air in the rooms.
The inlet valves are assembled on the external walls or windows. They are moisture sensitive and dose the fresh external air flow to the rooms. One inlet valve is sufficient for an area of 20 m2. On the internal wall of each room is mounted exhaust valve, through which the stuffy and wet air is evacuated to the air ducts. Exhaust fans provide forced air circulation, thus removing air exhaust. To provide unimpeded circulation, all internal doors must have certain distance to the floor or small opening in the lower end.