Issue overview

From helpdesk ticket 16916:

1. Zone Thermal Comfort Operative Temperature and Zone Operative Temperature are not always equal, why?
2. Zone Thermal Comfort Mean Radiant Temperature and Enclosure Mean Radiant Temperature are equal, so the difference is in the air temperature component.
3. Zone Thermal Comfort Operative Temperature and Zone Operative Temperature agree when the zone air temperature is constant. It appears that the thermal comfort calculations are using the air temperature from the end of the previous timestep?
4. Zone Thermal Clothing Surface Temperature (for Fanger) is an iterative solution.

https://github.com/NREL/EnergyPlus/blob/542d46babe10b7f4c4ea9e41d5e1d15357e4ba44/src/EnergyPlus/ThermalComfort.cc#L729-L743

5. Comparing it with the 7730 standard. The algorithm is very similar to the standard.
   I notice some lines to check against standard.

        // Compute the Corresponding Clothed Body Ratio
        state.dataThermalComforts->CloBodyRat = 1.05 + 0.1 * CloUnit; // The ratio of the surface area of the clothed body
        // to the surface area of nude body

        if (CloUnit < 0.5) {
            state.dataThermalComforts->CloBodyRat = state.dataThermalComforts->CloBodyRat - 0.05 + 0.1 * CloUnit;
        }

if (CloUnit < 0.5) is equivalent to If ICL <= .078. FCL is CloBodyRat variable.
In E+, CloBodyRat is not following the same logic if Clo < 0.5.

CloBodyRat= 1.05+0.1*CloUnit
if (CloUnit < 0.5)
   CloBodyRat = CloBodyRat -0.05 +0.1 * CloUnit = 1.0 + 2 * 0.1 * CloUnit
CloBodyRat should be 1 in this case.

6. Another difference is on the following line:

        // First guess for clothed surface temperature
        state.dataThermalComforts->AbsCloSurfTemp = state.dataThermalComforts->AbsAirTemp + (35.5 - AirTemp) / (3.5 * (CloUnit + 0.1));

The code is using CloUnit instead of CloInsul and the 3.5 is wrongly applied to 0.1.

Operating System (Multiple choices)

Any

Operating System Version

any

Version of EnergyPlus

User is testing with v9.4. Source code snippets are from v25.2 as of July 1.

Unmethours link or helpdesk ticket number

Helpdesk ticket 16916

Defect file

EnergyPlusDevSupport\DefectFiles