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What is best to model VRF with High Sensible Mode?

asked 2021-06-27 08:42:05 -0500

Keigo gravatar image

updated 2021-06-27 08:45:51 -0500

VRF with High Sensible Mode (I don't know what it is normally called in English) is often used in Japan to cool rooms with very high sensible heat load (very low latent heat load) such as Server rooms and Offices with desiccant dehumidifiers. Sensible heat ratio (SHR) is almost 1. The purpose of High Sensible Mode is to improve COP of VRF and save energy by setting refrigerant evaporation temperature high since there is no need for dehumidification by overcooling. The refrigerant evaporation temperature is set to about 13°C in High Sensible Mode whereas it is about 6°C in typical VRF. I don't have a good illustration of High Sensible Mode in English, and the following is an excerpt from DAIKIN's catalogue.

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My question is what is best to model this VRF with High Sensible Mode. If AirConditioner:VariableRefrigerantFlow can automatically change its refrigerant evaporation temperature to be the most energy efficient according to zone sensible and latent loads, I would prefer to use this. But if not, should I use AirConditioner:VariableRefrigerantFlow:FluidTemperatureControl and set Reference Evaporating Temperature for Indoor Unit? Or is there a better way?

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answered 2021-06-28 12:24:51 -0500

AirConditioner:VariableRefrigerantFlow is an empirical equation model. It uses performance curves to determine the capacity of the system at different operating conditions (i.e., Outdoor Dry-Bulb or water inlet Temp and coil entering air Wet-Bulb Temp). If these curves are available and accurately represent performance then yes this model can be used. See this paper for a discussion of the model can how to create the performance curves.

If other more detailed information is available then the AirConditioner:VariableRefrigerantFlow:FluidTemperatureControl model should be used. This model is typically used by advanced users to investigate VRF performance at different operating parameters.

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Asked: 2021-06-27 08:42:05 -0500

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Last updated: Jun 28