Comparison Issues between Air-Cooled Screw Units and Air-Cooled Modular Units

2025-03-02

I. Introduction to the System Overview

Air-Cooled Modular System
The air-cooled modular system is composed of outdoor units, various indoor terminal devices (fan coil units, air ducts, etc.), a water pipeline system, a circulating water pump, etc. Chilled water is sent to different areas through the circulating water pump and connected to terminal devices of different forms. Hot and cold air is sent out through the terminal devices and pipelines to adjust the indoor temperature. Each fan coil unit can also be independently controlled.
Air-Cooled Screw System
The air-cooled screw system is a traditional air conditioning system, which is composed of an air-cooled screw unit, indoor terminal devices (including fan coil units and air handling units), an air pipeline system, a water pipeline system, a circulating water pump group, etc. Chilled water is transported by the circulating pump to the terminals in different areas, and then sent to each room that requires air conditioning through the air supply pipeline.
II. Common Advantages
The air-cooled modular system and the air-cooled screw system have the following common advantages:
Investment Saving: Due to the same conversion between cooling and heating and the operating principle, both use water as the coolant to deliver cooling and heating to the indoors. The construction, as well as the costs of equipment and materials, are relatively low. The same system can be used for both cooling and heating, and no additional independent heating facilities are required, saving the initial investment.
Wide Application: It is especially suitable for air conditioning in villas, hotels, hospitals, office buildings, entertainment venues, restaurants, supermarkets, and other places.
Flexible Layout: Different types of indoor units can be selected to meet the indoor requirements of different decoration styles. When the decoration layout changes, the air conditioning can be configured according to the changes in the decoration layout.
III. Comparison between the Two Systems
The above are the similarities between the air-cooled modular chilled and hot water system and the air-cooled screw system. Below, the performance, technical and economic aspects of the above two air conditioning systems will be analyzed and compared.
Refrigeration System:
Since the air-cooled screw unit uses a screw compressor, which is different from the scroll compressor used in the air-cooled modular unit. Each unit has only one compressor, and the overall dimensions and weight of the entire unit are large, and the noise is very loud during operation. All the refrigeration work of the entire air conditioning system is undertaken by only one compressor. Once a failure occurs, the entire system will be unable to operate. If an additional unit is reserved, it will undoubtedly increase the cost of the entire system and cause unnecessary waste.

The air-cooled modular unit is composed of multiple air-cooled modular units with small dimensions and light weights. Each module has 2 to 4 scroll compressors. The refrigeration capacity of the entire air conditioning system will be shared among each compressor in each module. If a certain compressor or module fails, it will not affect the entire system. Repairing or replacing the compressor and the module will not affect the operation of the air conditioning system, and the cost is also very low. There is no need for a standby unit. Even if 1 to 2 modular units are reserved as standby, the increased cost is not much, saving the initial investment.
Due to the refrigeration principle of the screw compressor, the processing accuracy of its main compression components is very high, and the requirements for the compressor's lubricating oil are also very high. Therefore, in case of a failure, it will lead to high maintenance costs. The scroll compressor of the air-cooled module is small, and the costs of repair and replacement are very low, saving the maintenance costs.
The starting current of the screw compressor is very high, which will cause an impact on the power grid, and it needs to be preheated for a long time before starting to be used normally. The principle of the scroll compressor of the air-cooled module is simple. Since each compressor is very small, the system can be started sequentially during operation to avoid an impact on the power grid. The noise is also very low.
Operation and Control:
The control of the air-cooled screw system is complex:
The air-cooled screw system has various complex system configurations such as the main unit, pump group, valves, and high-voltage electricity. There are complex operation and inspection procedures before starting and running, which need to be completed through the coordinated cooperation of professional technicians from several trades. The operation is very complex. After starting, it also needs to be run for a period of time for trial operation, and it can only operate normally after confirming that there are no faults.
Since the air-cooled screw unit is large, and the main equipment such as the water pump and valves are all independently controlled, the control process of switching on/off and cooling/heating conversion is relatively complex. Each system is independently switched on/off and converted, and professional technicians need to be equipped for operation and maintenance.
The air-cooled modular system can complete the task of starting and running as long as it detects the water volume of the system and switches on/off the power supply. The whole process does not require the participation of professional personnel, which is simple and quick.
Engineering Design:
In the air-cooled screw system, in order to compensate for the heat exchange loss caused by the scale and dirt in the condenser, the compressor of the refrigeration unit has to increase its operating power. Due to the increase in power, the air conditioning system consumes more electrical energy to slow down the occurrence of the above phenomenon. The main units of the air-cooled screw system all have a large design margin, which will inevitably lead to the initial investment and actual operation cost being much higher than the theoretical calculation value.
The air-cooled modular system does not have such troubles. There is no need to consider too much the unnecessary design margin brought to the system by the operation loss, thus saving the actual investment and operation cost.
Installation, Debugging and Maintenance:
Due to the precise manufacturing of the air-cooled screw unit and the complex control process, there are also many data that need to be checked and tested. Therefore, the on-site debugging is particularly complex, and the technical requirements are high. Therefore, when debugging, not only professional debugging and maintenance personnel need to be equipped, but also comprehensive control and management system software need to be equipped for debugging.
Due to the precise and complex structure of the main equipment, the debugging workload is large and the cycle is long, and it is impossible to ensure the success of the first debugging.
Since there is a large amount of engineering work to be checked during the installation, debugging and maintenance of the air-cooled screw system, not only a large number of installation, debugging and maintenance personnel are required, but also the installation, debugging and maintenance costs are relatively high.
For the air-cooled modular chilled water system, the process design is relatively simple, and the workload of installation and debugging is relatively large, but the debugging process is simple. After the entire system is debugged once, it can be put into use.