Comparison of indoor air distribution and thermal environment for different combinations of radiant heating systems with mechanical ventilation systems

A hybrid system with a radiant heating system and a mechanical ventilation system, which is regarded as an advanced heating, ventilation and air-conditioning (HVAC) system, has been applied in many modern buildings worldwide. To date, almost no studies focused on comparative analysis of the indoor air distribution and the thermal environment for all combinations of radiant heating systems with mechanical ventilation systems.

Therefore, in this article, the indoor air distribution and the thermal environment were comparatively analyzed in a room with floor heating (FH) or ceiling heating (CH) and mixing ventilation (MV) or displacement ventilation (DV) when the supply air temperature ranged from 15.0°C to 19.0°C. The results showed that the temperature effectiveness values were 1.05–1.16 and 0.95–1.02 for MV+ FH and MV+ CH, respectively, and they were 0.78–0.91 and 0.51–0.67 for DV + FH and DV + CH, respectively.

The Predicted Mean Vote values were from 0.24 to 0.45 and from 0.11 to 0.43 for MV+ FH and MV+ CH, respectively, and from 0.01 to 0.23 and from -0.41 to 0.10 for DV + FH and DV + CH, respectively. Hence, MV + FH had the largest temperature effectiveness and Predicted Mean Vote, and DV +CH had the smallest values.

In addition, the vertical air temperature differences for MV+ FH and MV+CH were all within the comfort zone according to ISO 7730, but exceeded the comfort zone for DV + FH and DV +CH when the supply air temperature was less than 17°C and 19°C, respectively. The air distribution effectiveness values for MV+ FH and MV+CH were close to the recommended value for MV in the ASHRAE Standard 62.1, and those for DV + FH and DV +CH were slightly less than the recommended value for displacement ventilation.

The results in this article are relevant and useful in the process of selection and design of a hybrid system with a radiant heating system and a mechanical ventilation system in practice.