Design location

Equipment selection
Release date:2017-05-24 Source: Author:
Through the research and production practice, we believe that: the cooling device for scientific and rational design and matching composition, and through the main operating parameters of the system carefully, correctly and reasonable control of the control, can make the refrigeration unit in the most economical and fair work Conditions, safe and reliable operation, while achieving the largest cooling capacity, the most power consumption, the highest efficiency of the purpose of running.
The following is a brief talk about a few points in the design and selection of refrigeration equipment in the energy control technology, initiate, so that the majority of refrigeration users, more economical, fair, safe, energy-saving design and use of refrigeration equipment.
A good refrigeration project (cold storage) mainly by the insulation part (hexahedral insulation, the door), refrigeration compressor, auxiliary refrigeration devices, automatic control systems and other components.
One, the body of the insulation part
The current library insulation mainly by the two kinds of technology, one polyurethane foam spray, directly to the insulation material sprayed on the walls of the building; the other is the factory standardized production of polyurethane materials, cold storage insulation board. Ground insulation generally use XPS extruded board. Regardless of which insulation process is used, its role is to outdoor heat and indoor cooling capacity of the compartment, the internal cooling of the reservoir to protect, reduce the loss of cooling is its main role. In actual work, the general brick and concrete structure of the cold storage insulation, more use of on-site spraying insulation treatment, and large-scale steel cold storage and more use of cold storage board insulation. Of course, from the price analysis, spraying is certainly cheaper. The current spray price of about 700-800 yuan / ton, if the 100mm thick, 1 square price of 80 yuan or so. And good cold plate B1 level of its ex-factory price at least 160 and above.
Cold storage spray insulation cold storage board

First, the main components of refrigeration equipment, energy-saving selection

1.1 Selection of refrigeration compressor

1.1.1 Temperature range

Refrigeration equipment design in the choice of compressor, the first should consider the cooling equipment on the requirements of the temperature, while the user's cold situation should also be carried out in-depth investigation to understand, select the temperature requirements of the high temperature compressor or low temperature compressor. In the second generation of piston-type refrigeration compressors, taking full account of the different working conditions of the motor power and gas flow is different from the same displacement of the high temperature compressor and low temperature compressor are used different motor and valve plate combination of optimal design and manufacturing of. Low temperature compressor is never allowed to apply to the evaporation temperature is greater than -5 ℃ above the occasion to avoid the compressor motor overload; the other hand, in the low temperature field if the same displacement of the high temperature compressor, often due to motor efficiency, power factor Reduce the impact of the valve plate clearance caused by cooling capacity significantly reduced cooling, power consumption is also very uneconomical.

1.1.2 Cooling capacity

The size of the cooling capacity will be directly related to the one-time investment in engineering design, land area, energy consumption and operational economic effects. Usually the size of the cooling capacity is based on the user's heat load. Production situation in the situation vary widely, usually should be integrated to consider a one-time investment and operational economic effects. It should be noted that different users of the cold law is different, the energy prices around the different, and other factors, will affect the one-time investment in equipment and operating economic performance of the proportion of the design. Therefore, the design staff must fully investigate the actual situation of the local, the system of economic technology analysis, to make a comprehensive economic rational choice, must not simply apply the formula to select the formula to determine. Poor choice of design options will not only cause difficulties in handling and maintenance of refrigeration equipment, resulting in reduced efficiency, increased energy consumption, and potentially serious accidents.
1.1.3 Energy regulation

Usually the compressor is always selected according to the system's maximum cooling capacity requirements. In the actual production, the heat load is often changed with the external conditions, which proposed the compressor should be adjusted accordingly, so that the cooling capacity and the external heat load is always balanced, reducing the system evaporation temperature and pressure Fluctuates, thereby correspondingly reducing the temperature fluctuation of the object to be cooled.

For a single compressor, the simplest energy adjustment mode is intermittent operation, that is, when the required temperature reaches the compressor, the compressor stops running; when the temperature rises to the upper limit, the compressor will restart operation. Obviously this method is only used for small compressors, due to the power of more than 10kW compressor, the compressor motor will cause frequent activation of the power supply circuit voltage fluctuations, affecting the normal operation of other equipment, while the compressor even if not very frequent Repeated start will always have a fatal damage to the compressor damage.

For more than 4-cylinder multi-cylinder series of compressors, the use of each block closed 2 cylinder energy regulation, basically to meet the actual production requirements of the regulation, but from the energy point of view, this adjustment is clearly not ideal , Because the unloading cylinder does not produce refrigeration compression work, but the piston rod is still moving, there are still mechanical motion wear, the compressor power consumption is almost unchanged, rather than the ideal with the cooling with the same width, which So that the compressor in the energy-regulated part of the load to run and can not maintain full efficiency under the COP value, especially in the 50% load below the operation, the compressor will be more economical and energy saving.

If the hot air bypass adjustment mode, that is, with the system heat load decreases, the suction pressure decreases, when it is lower than the bypass valve set pressure difference, the bypass valve to open part of the high-pressure refrigerant gas directly to the suction Piping, so that both to further reduce the suction pressure, but also make the compressor net cooling down. Due to bypass the energy adjustment in the bypass of the refrigerant, the compressor to do its work and it did not produce effective cooling capacity, not to mention the bypass when the suction temperature will cause the compressor exhaust temperature is too high, may also pass The loss of refrigerant to spray the suction line to eliminate, and further caused the loss of the compressor cooling capacity, therefore, from the energy point of view does not advocate the use of this adjustment method, which is very uneconomical.

In addition there is the use of frequency control device for energy regulation, from the compressor using three-phase asynchronous motor angle can be a good solution to the cooling capacity and motor power always match the problem, but in a certain high and low speed range, piston compressor There is the opening of the valve movement law, lubricating oil and other issues, and frequency control device generated by a one-time increase in investment costs are not easy to accept.

Through the production and use of practice, we gradually familiar with the multi-machine parallel system, that is, in the same system using multiple compressors in parallel to replace a single high-power compressor, cooling equipment is to achieve a more reasonable way to adjust the cooling method to ensure that refrigeration equipment In the part of the load to run the high efficiency, to achieve energy-saving operation, which is particularly favorable for large cooling system. Table 1 shows the same system using a compressor and four compressor system energy consumption experimental comparison results.
Table 1 Comparison of single and four compressor systems operating energy consumption

100% load 75% load 50% load 25% load

Single system energy consumption 100% 86% 77% 67%

4 systems Energy consumption 100% 75% 50% 25%

4 systems Energy saving 0% 11% 27% 42%

It can be seen that when the partial load is smaller, the more the number of compressors is used, the more energy efficient the operation will be. At the same time the system in the multi-machine start-up, to avoid the impact of excessive fluctuations in the power grid, a comprehensive improvement of the cooling operation of the economy, security, and when more than one Taiwan compressor failure, you can also single Maintenance and the system can still be maintained.
Production of a variety of refrigeration systems in a part of the load to run the time, have a considerable proportion, therefore, the use of multi-machine parallel system on the operation of energy conservation also has considerable potential, it is worth to do in the design selection Analysis of the comparison. Of course, this will have its one-time investment to increase the space occupied by equipment and other adverse side. Therefore, whether the use of multiple systems and the number of specific selected number, should be based on the user's actual situation for further comparative analysis, a comprehensive measure and then determine the best fair design selection program.
It is generally recommended that in the design of larger refrigeration equipment, the number of units to be determined for the compressor configuration should be as small as possible to simplify the system and to facilitate manipulation, but the total number of stations should not be less than 2 units to ensure effective cooling of the heat load , As well as the maintenance of a single system to maintain the operation.
 Refrigeration compressor unit
1.2 Heat exchanger selection

1.2.1 Condenser

Air-cooled condenser, due to poor air heat transfer, the condensing temperature is often high, so that the condensing pressure increases, the refrigerator efficiency, energy consumption increased. Therefore, it is more suitable for summer outdoor temperature is not too high areas, or condensing pressure lower refrigerant. Its greatest advantage is that no cooling water is needed, especially suitable for use in water-scarce areas or water-supply areas.
Natural water temperature is generally low, and the water heat transfer performance is excellent, so the condensation temperature of the water-cooled condenser is relatively low, which is the compressor cooling capacity and operating economy are more favorable, is currently in the industrial refrigeration system has been widely used , In order to save water resources, the widespread use of cooling water tower device, so that the condenser of the water cooling cooling, water cooling condenser repeated use.

Evaporative condenser, which utilizes the latent heat of vaporization when the cooling water evaporates to absorb the heat released by the refrigerant, thus achieving a small amount of cooling water for the transfer of condensed heat. General water cooled condenser 1kg of cooling water can take away 16.75 ~ 25.12 kJ of heat, and 1kg of water at atmospheric pressure can take away about 2428 kJ of heat, so the evaporative condenser theoretical water consumption is about the general water-cooled condenser 1%. In fact, taking into account the loss of blows, sewage and other losses, the water consumption is only about 5% to 10% of the general water-cooled condenser.

Evaporative Condenser Due to the fact that the cooling water in the condenser is in the sensible heat transfer stage, the condensing temperature may be closer to the wet bulb temperature of the air, thereby reducing the compressive energy consumption. Through the study and analysis of cold storage, it is shown that the deviation between the condensation temperature and the air wet bulb temperature is 8.3 ° C or less. Under such conditions, the use of evaporative condenser system and cooling tower and shell-and-tube condenser compared to the system, the compressor power consumption can save more than 10%; compared with the use of air-cooled condenser system can save More than 30%. Because of its own play a cooling tower role, so the initial investment will actually be lower than the water-cooled condenser and cooling tower integrated initial investment.

Condenser heat transfer area is another important part of the design selection, the design should take full account of the domestic design and manufacture of refrigeration units and users in the use of maintenance and awareness of the general level of awareness of the status quo, the appropriate choice of larger condensation The area is still more economical and practical, more in line with China's national conditions.

In summary, all kinds of condensers have their advantages and disadvantages. For certain applications, the direct consequence of using different condensers is that the cooling temperature is different from the pressure, and the chiller operates differently. However, most of the current domestic users in the actual choice of condenser, often on the impact of different energy consumption of the condenser to consider little difference. In fact, the impact of the choice of the condenser on the energy consumption of the refrigeration unit must arouse our attention. In the design of the equipment, a comprehensive technical and economic analysis of the different schemes with different condensers should be carried out, taking into account the initial investment and the installation location environment , Manipulation and other aspects of maintenance factors, and then choose the best fair program.
 
1.2.2 Evaporator

In the actual engineering equipment design, the choice of evaporator mainly consider the evaporator type and heat transfer area two factors. In recent years, the design of the heat exchanger has a consistent tendency to adopt a smaller heat transfer temperature difference, when the heat transfer is constant, the heat transfer temperature difference must increase the heat transfer area, heat transfer area increases Means increasing investment and reducing operational costs. With the prominent contradictions in energy shortages, countries around the world have put forward higher demands on energy conservation and adopted corresponding policy measures. Therefore, the appropriate increase in investment can reduce the energy consumption of annual operation and achieve the goal of energy saving. The increase in operating costs, due to energy savings and increase the payback period will be gradually shortened, the ultimate high economic benefits. Heat exchanger on the operating costs of increasing attention, plate heat exchangers and other new efficient heat exchanger is being continuously developed and applied.

1.3 throttle device selection

The throttle device has no external power output, so there is no concept of efficiency consumption, but the operating characteristics of the throttle device directly affect the cooling performance of the refrigeration unit, affecting the efficiency and energy consumption of the device. The improper selection of the thermal expansion valve will result in a decrease in the evaporation area of the evaporator, a decrease in the efficiency of the refrigeration unit, an increase in energy consumption, and even a fatal damage to the compressor.

Correct choice of adjusting the expansion valve is an important part of the energy saving of the refrigeration unit. The capacity of the thermal expansion valve is changed with the working conditions. When selecting the capacity, the heat expansion valve performance table provided by the manufacturer should be selected. However, it is necessary to pay attention to the balance of the thermal expansion valve, the evaporation temperature, Pressure and valve inlet liquid temperature and other factors on the expansion valve capacity to be amended, so as to ensure that the thermal expansion valve and the cooling device is well matched, so that the cooling device in the best running state, to achieve the purpose of energy efficient.
At present, most users and engineers in the country in the refrigeration equipment, engineering design and construction, are more or less focus on the compressor host and ignore the concept of auxiliary equipment practices. In the actual selection of heat exchangers, throttle devices and other refrigeration system accessories, often rarely consider the auxiliary configuration caused by cooling equipment operating energy consumption differences and the impact on operational safety. In China's refrigeration system auxiliary equipment configuration performance significantly behind, and therefore restricts the performance of the compressor host to give full play, even the compressor host will form a fatal accident. In the emphasis on the compressor at the same time, heat exchangers, throttle devices and other auxiliary accessories to optimize the choice of energy on the impact of refrigeration equipment, we must pay great attention!
 Expansion valve
Second, the main operating parameters of the refrigeration system energy saving control adjustment

In the actual operation of the refrigeration equipment and systems engineering, we are familiar with not only should the refrigeration system should be adjusted to a reasonable operating range to meet the refrigeration process requirements to maintain its safe and normal operation, but also should be able to further adjust the refrigeration system to the most Good running status, to achieve efficient energy-saving operation purposes, improve the level of energy-saving refrigeration equipment operation.
2.1 evaporation temperature and evaporation pressure

In the design of the refrigeration equipment, the progressive evaporation temperature will reduce the compression ratio of the refrigeration system and reduce the power consumption, which is very beneficial to the energy saving. The subject is the evaporation temperature depending on the object being cooled, and the adjusted evaporation temperature must be conditional on the refrigeration process requirements that do not affect the subject being cooled. However, in the adjustment of the operation of the refrigeration device, should pay attention to observe, take appropriate measures in time, such as appropriate defrosting, the appropriate increase in the amount of liquid, the evaporator to remove oil and dirt removal, the implementation of effective energy regulation of the compressor, so The evaporation temperature is stable at the design temperature, avoiding the evaporation temperature is unnecessarily too low or very necessary.
From the energy-saving point of view, the appropriate progress of the evaporation temperature is economically fair, the calculation shows that when the wall temperature of -25 ℃ instead of -30 ℃ library temperature, due to the evaporation temperature, will save energy up to 9.8%. Therefore, for the storage period is short, the quality of low temperature requirements are not high, you can properly improve the evaporation temperature, to achieve energy saving effect. In addition, the general refrigeration devices are designed at full load, while the actual operation at full capacity and

Company

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Hao Cool Refrigeration is the leading designer and manufacturer of cold storage and refrigeration equipment. Within the high quality iulated panels, energy-efficient refrigeration systems, Combined yea of exteive experience and our co-worke’effort that makes Hao Cool to be the Leader in the field of cold storage cotruction and refrigerated warehouse logistics. With capabilities range from a small cold rooms to a large refrigerated warehouse, Hao Cool Refrigeration can meet any
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