Human Thermal Comfort for Architectural Analysis

About the ThermoAnalytics Human Comfort Module

The ThermoAnalytics Human Comfort Module is a collection of user routines and property database that is available under a separate license to operate with RadTherm, RadThermIR or MuSESPro to simulate the thermal response of a human body when exposed to environments with significant thermal loads. The additional biothermal phenomena, including thermoregulatory mechanisms, are fully handled by this module, which functions as a dynamically linked library (DLL). The Human Comfort Module can accurately calculate metabolic rates and blood perfusion energy rates, as well as respiratory heat losses and evaporation from the skin. The module is an active component operating within RadTherm or MuSESPro during the solution process, and it incorporates a localized clothing database. The body core temperature, as well as localized body segment temperatures are accurately predicted; and based on these values, a thermal comfort index using the ASHRAE seven-point scale (-3 to +3), is computed.

Common Applications

The Human Comfort Module is useful for determining the comfort of humans in the design of clothing, aircraft, vehicles, and buildings; and can also be applied to address the safety concerns of humans working in thermally significant environments such as firefighters, pilots, foundry workers, and soldiers. The Human Comfort Module operates with Version 9.0 of RadTherm, RadThermIR and MuSES. For certain applications, such as the Federal Aviation Administration certification of aircraft thermal safety for pilots and passengers, the Human Comfort Module has been validated against the ASHRAE two-node model.

Human Thermal Comfort in an Office Environment with Solar Loading Through SE Facing Window, Phoenix, AZ

This sample model demonstrates a human thermal model seated and working on a computer at a typical L-shaped desk, enjoying a hot cup of coffee as his internal feedback loops are stabilized. The model is set up as a transient analysis starting in the early morning hours and proceeding through noon. The human virtual model faces southeast, with a window that transmits solar loading directly to him and the office equipment surrounding him. He is exposed to a stable office air temperature and exchanges radiation with the walls, desk, chair back, and computer LCD display. Using a new feature in Version 9.0, Face-to-Face Conduction, his legs and buttocks are in direct conductive contact with the chair seat, and his hand is in direct conductive contact with the external surface of his coffee cup. Inside the cup is a fluid part with an assigned initial temperature of 80ºC to capture the transient cool down of the coffee from an appropriate post-brew and pour temperature (our virtual friend having wisely brewed at the optimal temperature of 95ºC).

The southeast wall of the room is exposed to the natural outdoor environment, and the other three walls are given internal boundary conditions, representing a single office within a larger building without having to explicitly model the rest of the building. The environment was defined as Phoenix, Arizona, in August, so the solar intensity and external ambient temperature are quite severe.

Geometry and Mesh

The office, desk, PC, keyboard, mouse and chair were created in Alias Maya software, the human model was created in Poser, and all parts were meshed using ANSA. The human model was parted out based on clothing and physiological boundaries. For users that require human models to be posed and in contact with specific geometry or environments, ThermoAnalytics now offers engineering services to set up and mesh human models perfectly suited to any furniture, cockpit, vehicle cabin, or architectural environment. Contact us to review your needs in detail.

Boundary Conditions for the human model were imported from an ASCII file through the Human Comfort Module DLL, called boundaryconditions.txt. The Human Comfort Module supports layered clothing; the model is setup with briefs under trousers, for example, and a T-shirt under the dress shirt for upper arms, shoulders, upper abdomen, and lower neck.

Boundary Conditions for the human model were imported from an ASCII file through the Human Comfort Module DLL, called boundaryconditions.txt. The Human Comfort Module supports layered clothing; the model is setup with briefs under trousers, for example, and a T-shirt under the dress shirt for upper arms, shoulders, upper abdomen, and lower neck.

Thermal Sensation (TS)

The plot below represents the pseudo-steady-state value of TS for the virtual human in the office. TS considers only the temperature state at any moment in time, and the thermal history of the ‘human’ is not considered. It uses the ASHRAE scale below: -3 represents a human feeling very cold, +3 represents very warm, and 0 represents thermally comfortable.

Validation againt the PMV Method

One validation exercise we can easily carry out for the ThermoAnalytics Human Comfort Module is to compare its results with the much simpler but well-established PMV method, which is straightforward. Its only input parameters are whole body values of clothing insulation, metabolism, external work, air temperature, mean radiant temperature, air velocity, and relative humidity. In brief, this method can be described as a simple energy balance, in which a human comfort index is estimated from a difference in heat generated by the human body with the heat lost from the body to the surroundings.