【 Weak current College 】 VRV design problems---Power By 【 China power house network 】

Preface: VRV system variable refrigerant flow air conditioning system, starting from the early 1990s, has been developing rapidly, due to the system by the use of flexible, energy-saving and easy to install, and other advantages that make the system a lot used in Office buildings, hospitals, etc. But because VRV system is a modular air conditioning system mode, unlike traditional centralized air-conditioning system, there are many differences compared to. Author through summary conditioing design experience gains and losses, to talk about.

1 cold energy attenuation

Usually VRV systems, indoor and outdoor machine are connected through refrigerant pipes, refrigerant piping length and indoor and outdoor unit height difference affects the amount of cold and air conditioning systems. To Japan Daikin VRV system the company's products, for example, the product description in the description: indoor and outdoor machine between the refrigerant tube length to 150m, indoor and outdoor machine height difference between May to 50m, indoor height difference between permissible 15m. These are design should ensure that the limit value in the range of design-time to note that with the refrigerant tube length and indoor height difference, the cold energy attenuation vary greatly. Daikin company give cold energy attenuation as in Figure 1. You can see from figure: when the indoor unit is outdoor unit, height difference < 10m, refrigerant tube equivalent length < 10m, capacity correction factor about 1.0; when indoor height difference reached 30m, refrigerant tube equivalent length reaches 30m, capacity correction factor about 0.9; when indoor height difference reached 50m, refrigerant tube equivalent length reaches 90m, capacity correction factor about 0.72.

Thus, in the design to take into account the correction factor of capacity, in the system design is to try to make a system for indoor and outdoor machine the shortest distance between the minimum, the altitude difference on the height difference is big, the pipeline long system to appropriately increase the capacity of the unit, so as to guarantee the effectiveness of air conditioning use.

2 fresh air issues

The issue has been the fresh air conditioing design difficulties, but also to a large extent restrict further VRV systems, the following simple introduction to several pros and cons of fresh air:

2.1 conditioing General indoor unit as a new fan for fresh air

This method because the system is relatively simple, the application in the project. Because conditioing of indoor coil is based on the design of air conditioning air status, not by fresh State design, so on the one hand, indoor unit cannot be fresh air to the indoor part of the State, require fresh air load burden by indoor unit, on the other hand in the outdoor temperature is high, the pilot-in-time outdoor overload, over current protection.

2.2 adopts thermal switch as a new fan

Use the full-heat exchanger in the fresh air from the room supplement, the use of the indoor air of chilling to cooling of fresh air, the efficiency of the recovery of cooling capacity is 60%-70%, 28% of energy. This method is VRV fresh air system is better, in a real application, the large space conditioning system adopts the full-heat exchanger, air supply and exhaust pipes are easy to set up, and in the corridor-small Bay office buildings, hotels and other places, at the same time set the fresh air and exhaust pipe is more difficult, and can be combined with engineering, will exhaust system set settings. For example set toilets exhaust or corridor ventilation, so you can simplify the air-conditioning piping. In addition, when using full-thermal switch also note the noise impact.

2.3 VRV manufacturers provide fresh air machine

These new fans are usually designed by fresh State, increased the unit number of the row of coils, fresh air into the room status points. But this means higher construction cost and affect the application in the project, on the other hand, the outdoor temperature is high, the compressor long continuous operation, affect the life of the unit.

2.4 sets the air-cooled heat pump units to provide cooling and fresh air system

This method is to use fresh air system and VRV systems, fresh air system with hot and cold water system, which ensures that the air flow ventilation system and cooling capacity. In larger projects, especially with the public part of the podium projects more reasonable, this kind of project main building set conditioing, podium for air conditioning and ventilation system in the main building of heat and cold sources by providing air-source heat pump unit, which also reduces construction cost. But this method takes 2 types of air conditioning system, running on a more cumbersome management, does not fully reflect the flexible VRV systems, energy-saving features.

2.5 using direct evaporative air conditioners, roof machine as a new fan

Such methods and 1 method, which uses ordinary conditioing indoor unit as a new fan of principle is the same, there is also insufficient cooling, as well as host overload problems, serious or even burn machine phenomenon occurs.

3VRV air-conditioning system control

VRV systems control system is more flexible and convenient system can be equipped with various remote control (wired or wireless, simple remote control, remote control, remote control, Central Hotel, etc), there are also extended converter, you can centralize control of 64, up to 1024 conditioner, in addition to building management system. In the design-time selection may be made in accordance with the requirements of the different control methods, engineering instance often to reduce project cost and not focus on the control system, in fact, VRV air-conditioning control system than the central air conditioning system settings control the system more convenient, economical, without increasing too much investment can achieve very good control effect. In addition to engineering in order to reduce the cost and often 1 bedroom in the same remote control several indoor unit, this will cause the room temperature is too cold thermal phenomena, so each remote control best control 1 indoor unit.

VRV system production technology to constantly improve, capacity continues to increase, while the project cost is gradually reducing, believe conditioing will have a broad prospects.BR>