Abstract
This paper developed an algorithm that controls the supply air temperature in the variable refrigerant flow (VRF), outdoor air processing unit (OAP) system, according to indoor and outdoor temperature and humidity, and verified the effects after applying the algorithm to real buildings. The VRF-OAP system refers to a heating, ventilation, and air conditioning (HVAC) system to complement a ventilation function, which is not provided in the VRF system. It is a system that supplies air indoors by heat treatment of outdoor air through the OAP, as a number of indoor units and OAPs are connected to the outdoor unit in the VRF system simultaneously. This paper conducted experiments with regard to changes in efficiency and the cooling capabilities of each unit and system according to supply air temperature in the OAP using a multicalorimeter. Based on these results, an algorithm that controlled the temperature of the supply air in the OAP was developed considering indoor and outdoor temperatures and humidity. The algorithm was applied in the test building to verify the effects of energy reduction and the effects on indoor temperature and humidity. Loads were changed by adjusting the number of conditioned rooms to verify the effect of the algorithm according to various load conditions. In the field test results, the energy reduction effect was approximately 15–17% at a 100% load, and 4–20% at a 75% load. However, no significant effects were shown at a 50% load. The indoor temperature and humidity reached a comfortable level.
Highlights
The variable refrigerant flow (VRF) system was developed in Japan in 1982 [1], and entered the heating, ventilation, and air conditioning (HVAC) market in Europe in 1987 [2]
The reason for the increased cooling capacity of the indoor unit was because of the refrigerant, which was supplied to the outdoor air processing unit (OAP) previously, was supplied to the indoor units, as the OAP capacity was reduced as the supply air temperature was increased
This paper developed the control algorithm for the supply air temperature in the OAP for VRF-OAP systems, and verified the effects by applying the algorithm to a test building
Summary
The variable refrigerant flow (VRF) system was developed in Japan in 1982 [1], and entered the heating, ventilation, and air conditioning (HVAC) market in Europe in 1987 [2]. The VRF system market has expanded to China, South Korea, United States, Brazil, Turkey, and India. The market continues to grow, numbering 1.3 million units in 2014 and its market value has reached. The VRF system consists of a single outdoor unit and multiple indoor units. The main components of the outdoor unit are a compressor and a condenser, and those of the indoor unit are evaporators and expansion valves. The outdoor unit and each of the indoor units are connected with the refrigerant
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