Ningbo, China
Ningbo, China

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Tu Q.,Aux Electrical Co. | Zou D.,Ningbo University | Deng C.,Aux Electrical Co. | Zhang J.,Aux Electrical Co. | And 4 more authors.
Applied Thermal Engineering | Year: 2016

A set of 14 HP variable refrigerant flow air conditioning system (VRF AC) with multi-compressor has been designed, and the output capacity control strategy of compressor(s) including the switching control model of standard compressor has been built. In the output capacity control model, a certain suction pressure is used as the pressure control target to adjust the output capacity of compressors, and a little pressure fluctuation is taken into account to amend the target pressure. Furthermore, in the compressor switching control model, the most favorable operation frequency region is determined on base of the energy efficiency characteristic and noise characteristic of the compressor. And, in order to solve the large fluctuation problem of the system running and frequent ON-OFF action of the standard compressor, the equal output capacity switching principle can be used to determine the thermo-on and thermo-off switched frequency points, and control the switching process of the compressor. Experiments demonstrate the feasibility of this control strategy to ensure the stability and reliability, improve the energy efficiency and reduce the compressor noise. © 2015 Elsevier Ltd. All rights reserved.


Tu Q.,Aux Electrical Co. | Feng Y.,Aux Electrical Co. | Liu Q.,Aux Electrical Co. | Li C.Z.,Aux Electrical Co. | Du P.,Aux Electrical Co.
Building Services Engineering Research and Technology | Year: 2015

Defrosting is an important controlled event of variable refrigerant flow air conditioning system (VRF AC). The whole course includes defrosting preparation phase, defrosting execution phase, defrosting end preparation phase and pump-down residual running phase. The defrosting control function can make a great influence on the performance of variable refrigerant flow air conditioning system, whose elements are composed of a certain controlled event, controlled components, executed conditions, controlled time, controlled courses and control logic. A sequence diagram is adopted to express the defrosting dynamic process and the control models of execution conditions on defrosting arrival, defrosting end and pump-down residual running end have been built. Thus, the defrosting control function has been formed based on the model and sequence diagram. The defrosting experiments demonstrate that the built model and sequence diagram can scientifically and accurately express the defrosting control function.Practical application: Defrosting is an important controlled event of variable refrigerant flow air conditioning system. It is difficult to describe the complex controlled course, which is composed of defrosting preparation phase, defrosting execution phase, defrosting end preparation phase and pump-down residual running phase. A sequence diagram can be adopted to express the defrosting dynamic process and the control models of executed conditions on defrosting arrival, defrosting end and pump-down residual running end have been built. Thus, the defrosting control function has been formed based on model and sequence diagram. © The Chartered Institution of Building Services Engineers 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

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