Approximately 10 years ago, in our country, first a single, then a wide practical use of air conditioners began to create comfortable conditions in rooms for various purposes. In the vast majority of cases, these were split systems, it was often possible to observe how up to two hundred of their outdoor units appeared on the facades of reconstructed administrative buildings. Split systems cannot maintain the given gas composition of air in the room, regulate its humidity. Their main function is air cooling.
Later, for objects such as hotels, business centers and other similar buildings that require a certain microclimate for their operation, vapor-compression water-cooling machines (PKHM), supply chambers for supplying fresh outside air and fan coils began to be used.
Now the demand for refrigeration for air conditioning systems continues to grow. The required cooling capacity for new large facilities, such as water parks, shopping and entertainment centers with an area of 30,000 — 100,000 m 2 , storage areas of logistics terminals for the processing of pharmaceutical products, loose tea and tobacco increases to 5,000 — 8,000 kW. The use of vapor compression machines at such facilities gives rise to a number of technical problems, the solution of which significantly increases the cost of producing “cold”.
It should be noted that the role of air conditioning systems for the mentioned objects is also increasing. From systems that only provide comfortable conditions in the premises, they become part of the technological process for them. So, every minute of a person’s stay in a shopping center increases his income, so special technologies are being developed to keep customers in the hall. And air conditioning systems no longer exist as an additional option — they contribute to the development of the profitability of enterprises and become one of the main technological systems.
We can assume that the trend of growth in the area of a single construction object has finally been determined. The appearance of super-large objects in Moscow, and then in St. Petersburg, indicates that over the next 3–5 years this trend will spread to other Russian cities. Thus, if the construction of facilities with an area of 30,000 — 100,000 m 2 becomes a trend, it is useful to develop a principled approach to the refrigeration systems of these facilities.
All engineering systems of any object are connected with each other either functionally or through a control system. Considering options for solving the problem of refrigeration supply, it is necessary first of all to take into account how the issues of heat and electricity supply are resolved. The problem of heat supply of large objects is usually solved by installing an autonomous boiler house. The solution to the problem of power supply, and we are talking about megawatts of electric power, is extremely difficult and expensive to solve. In the event that the facility is equipped with an autonomous gas boiler, then for refrigeration systems with a required cooling capacity of 500 kW there is an uncontested solution — absorption chillers (ABHM).
Absorption Chillers: all models
The first and main advantage of the absorption refrigeration machine is that it does not consume electricity for the implementation of the refrigeration cycle. Electricity is consumed only for the movement of media — the operation of pumps and fans. In this case, the point is not that electricity is expensive for the consumer, but whether it is possible to connect to the grid, and if possible, the cost of “connecting to the grids” of JSC “Lenenergo” in some cases reaches 1000 US dollars per 1 kW . Similar problems may arise in other cities supplied with electricity from RAO UES of Russia.
The next advantage is economic. As can be seen from Table 1, the initial investment costs for absorption chillers are significantly lower than those for vapor compression chillers. From the ratio of operating costs (see Table 2), the second important conclusion follows: the operation of absorption machines is almost two times cheaper than the operation of vapor compression machines. The importance of this conclusion will become clearer if we bear in mind that, according to the regulations, machines will operate for 20 years before a major overhaul.
It was noted above that ABKhM works on hot water supplied
from an autonomous boiler house, which is usually turned off during the warm season. The operation of the absorption refrigeration plant increases the load factor of the boiler house, thus reducing its payback period, which in turn increases the efficiency of the investment.
Another important advantage of absorption machines is the low noise level during their operation. The intrinsic noise level of absorption plants with a power of up to 1500 kW does not exceed 65 dBa. In addition, they meet the requirements of the Montreal and Kyoto protocols, i.e. do not contribute to the destruction of the ozone layer and global warming. absorption machines do not use refrigerants, the leakage of which is the cause of the destruction of the ozone layer.
From the material of the article, the reader may form an opinion about the presence of some kind of panacea in the field of refrigeration: cheap, simple, environmentally friendly and almost silent. All this is true. However, there are some “buts”. Absorption refrigeration units have a greater mass than vapor compression ones, and this mass must be distributed when placed on the roof of a building. The ABKhM circuit includes a cooling tower of significant size and weight, the operation of which is accompanied by noise, then silencers and acoustic screens may be necessary in residential areas. In some cases, instead of cooling towers, functional and decorative fountains are arranged. However, the cost of the fountain exceeds the cost of the cooling tower. A cooling tower or fountain requires make-up water to operate. For our example, the maximum make-up water flow is up to 3.4 m 3 /h It also needs to be received and submitted.
Thus, it becomes obvious that reducing investment costs by almost three times, and operating costs by about two times, is not as easy as it might seem at first glance. However, there are some interesting engineering solutions to overcome some of the inconsistencies when considering the whole complex of building engineering systems, rather than an isolated refrigeration supply system.
And the last. The absorption technique, which is really attractive to investors, also has a certain social component. Reducing investment and shortening the payback period of the project unwittingly contributes to lower prices in the consumer market, in which the development engineer himself acts as a buyer of goods and services.
Table 1. Comparison of the initial cost of a paracompression refrigeration machine (PKHM) and an absorption refrigeration machine (ABHM) with a cooling capacity Q o =1000 kW
Paracompression refrigerating machine (PKHM)
Absorption chiller (ABHM)
Approximately $200 per 1 kW
Total: $200x1000= $200000
ABHM for 1000 kW — $150,000
Cooling tower — 15% of the cost of ABCM
Total: 50000+15%x150000= $172500
Required electrical power:
Total cost of connection to the power grid:
If all investments in an autonomous boiler house have already been made, no additional costs are required
Table 2. Comparison of operating costs when using a paracompression refrigeration machine (PKHM) and an absorption refrigeration machine (ABKhM) with a cooling capacity Q o =1000 kW
In both options, the electricity consumption of pumps and fans (they should be approximately equal) is not taken into account
Paracompression refrigerating machine (PKHM)
Single stage absorption chiller
Taking the integral load of the refrigeration machine equal to 0.5 of the nominal refrigeration capacity (excluding night time, weekends), we determine the costs for the operation of the PCM, based on the cost of electricity 1.45 rubles / kWh.
They make up ≈ RUB 689,000
Single stage hot water absorption chillers with t w u003d 90.98 ° С, have a thermal coefficient
ς = Q 0 /Q G = 0.75,
where Qg is the amount of heat entering the machine from the heating medium.
It follows that in an autonomous boiler house it is necessary to burn a certain volume of natural gas to obtain this amount of heat, namely:
Q G = Q 0 / 0.75 u003d 1,000 / 0.75 u003d 1330 kW.
Assuming the efficiency of the boiler house equal to 0.9 with the calorific value of natural gas ≈ 35,000 kJ/m 3 we determine the total gas consumption for the warm period of the year:
V = 1330 × 120 × 0.5 × 3600/35000 = 197,000 m 3 ,
those. practically the consumption of natural gas for the entire warm period of the year is 200,000 m 3 . At a gas cost of 1.85 rubles. per m 3 its cost will be RUB 370,000