Brief introduction of various systems and comparison of modular units with other units. (1), modular unit modular unit: It is developed on the basis of VRV system. 1985, invented and patented by Jiefeng Group of Australia. It changed the traditional Freon pipeline into water pipeline, combined the indoor unit and outdoor unit into a refrigeration unit, and changed the indoor unit into a fan coil unit. The refrigeration process is realized by heat exchange of cooling water. Modular machine is named because it can automatically adjust the number of starting units according to the requirements of cooling load and realize flexible combination. 1, the unit adopts modular design, and the modules are connected by water pipes and wires, which is flexible in combination and convenient to install; It is very suitable for occasions that need hierarchical partition control. 2. The modular air-cooled (hot) water units of Changjiang Bureau are composed of several modular air-cooled (hot) water units. Each unit module has the same form and performance, with a refrigeration capacity of 68KW, and two completely independent refrigeration systems with a refrigeration capacity of 34KW respectively. In this way, the problems that other units can't solve can be solved by the unit step by step, that is, the output of the unit keeps the best match when the load changes from the minimum to the maximum. The impact on the power grid is small. 3. Modular system, the control computer will run the necessary number of modular units according to the changing heat load, so that the refrigeration output of the units is consistent with the required load. And each working refrigeration loop runs at the highest efficiency, so that no matter how the load changes, the efficiency of the unit remains stable, and even in the low load state, the output of the unit remains the best match. Therefore, the annual operation power consumption is reduced. 4. The refrigeration systems in the unit are independent of each other, and a module of the unit or a system in a module can be independently overhauled, which does not affect the use of the whole machine and is convenient to maintain; 5. No special maintenance is required during use; 6. Reliability and standby capacity: If a refrigeration circuit fails, the computer will instruct the failed circuit to stop running and start the next standby circuit, so that the unit can maintain stable refrigeration output. And the faulty circuit can be overhauled while the unit keeps running. This operation control enables the unit to obtain the best reliability and self-provided capacity. However, any small fault of the traditional unit may cause the whole machine to lose its working ability. There is no need to increase the standby unit, which greatly reduces the initial investment. 7. Air-cooled design enables the unit to be installed on the roof, balcony or outdoor courtyard without special computer room. Save cooling tower, cooling water pump, cooling water pipeline system and other facilities for users and reduce civil engineering investment. 8. Air-cooled heat pump design, no matter in cold or warm winter, there is no need to increase heating boilers. (2) Screw chiller: Screw chiller is a large and medium-sized refrigeration equipment that provides chilled water. It is often used for air conditioning in national defense scientific research, energy development, transportation, hotels, restaurants, light industry, textiles and other departments, as well as chilled water in water conservancy and electric power engineering. Screw chiller is a complete refrigeration system consisting of screw refrigeration compressor unit, condenser, evaporator, automatic control elements and instruments. It has the advantages of compact structure, small volume, small floor space, convenient operation and maintenance, stable operation and so on, so it has been widely used. Its refrigeration capacity ranges from 150 to 2200KW, which is suitable for medium and large projects. 1, single-screw unit has a large capacity, which is generally used in large and medium-sized projects, and is not suitable for occasions requiring hierarchical and zoning control; 2. The operation mode of the main engine is full open or full stop, which has great influence on the power grid; 3. The regulation ability is poor under partial load, especially when the load is below 60%, the coefficient of performance (COP) drops sharply, and it is generally only suitable for operation in the load range of 60%~ 100%. High operating cost; 4. High maintenance cost; 5. It is required to arrange special personnel for maintenance during use; 6. The screw unit itself does not have the standby capacity, so it needs a standby unit, which greatly increases the initial investment. 7, screw machine in the process of using noise is bigger. (3) Lithium bromide absorption refrigeration unit: Using heat energy as power, water as refrigerant and lithium bromide solution as absorbent, refrigerant water above 0℃ is prepared, which can be used as the cold source of air conditioning or production process. Lithium bromide absorption type is driven by thermal energy, and there are three common types: direct combustion type, steam type and hot water type. Its refrigeration capacity ranges from 230 to 5800KW, which is suitable for medium and large-scale and extra-large-scale projects. 1, the service life is shorter than that of compression type; 2. Large steam consumption and low thermal efficiency. The thermodynamic coefficient is about 0.6 for single effect, about 0.2 for double effect 1.2 for direct-fired type, and about 0.6 for direct-fired type. 3. The operation is complicated; 4. In the presence of non-condensable gas, lithium bromide has serious corrosion to metals, which requires strict sealing and corrosion protection; 5. Oil storage and transportation devices are needed for oil absorption refrigeration, which brings hidden dangers to fire safety. (4) VRV system: VRV system: short for variable refrigerant flow system, namely variable refrigerant flow system. It is in the form of a group of outdoor machines, consisting of functional machines, constant speed machines and frequency converters. By connecting outdoor units in parallel, the refrigeration pipeline is centralized into a pipeline system, and the appropriate indoor unit capacity level difference can be conveniently selected according to the capacity matching of indoor units, that is, a group of outdoor units can connect up to 30 indoor units. Indoor units include ceiling embedded, wall mounted, floor mounted, etc. Different indoor independent machines can be connected to the refrigeration circuit and can be controlled independently. The minimum capacity of the indoor unit is 0.6KW and the maximum capacity is 3.75KW. The capacity of the indoor unit can be adjusted within the range of 50% to 130% of the outdoor unit capacity. The initial investment of 1 and VRV systems is 40%~50% higher than that of modular units, and the cost saved can be enough for the owner's air conditioning electricity bill for five years; 2. The refrigerant used in 2.VRV system is R22, which is odorless, nontoxic and nonflammable at normal temperature and pressure, and is harmless to human body. However, when the indoor R22 concentration is high, the oxygen content in the air will decrease, thus affecting people's breathing. The refrigerant pipeline of VRV system is long and concealed, and the refrigerant flow is large. Once a leak occurs, it will be difficult to find the leak point and the maintenance cost will be high. The indoor medium of modular unit is low-pressure water, which is not easy to leak, with low installation and use cost, no need to replenish expensive Freon regularly, and low maintenance cost. 3. The electronic control system of 3.VRV system is complex, with high technology content, difficult maintenance and high cost; Modular unit does not exist.
Comparison of modular unit, VRV system, screw unit and lithium bromide unit: initial investment and operating cost of air conditioning system; Space occupied by equipment and pipelines; Main engine variable load control; Indoor temperature control accuracy; Noise construction and host installation; Maintenance cost of spare capacity of indoor pipeline medium; Specially assigned person to manage the air source module unit; Small, medium, easy, low, simple, low, difficult and strong; VRV-free frequency conversion unit; Small, easy and high; Special professional fluorine, high, easy, medium and high; Air-free screw unit; Medium, difficult, simple,