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.
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.
|
Part # |
Part Name |
Compartment |
Clothing ID |
Description |
|
1 |
Thorax |
Thorax |
5,2 |
#T-Shirt and long sleeve shirt |
|
2 |
Feet |
Feet |
101,106 |
#Dress socks, shoes |
|
3 |
Legs |
Legs |
30 |
#Straight long loose denim trousers |
|
4 |
Face |
Face |
0 |
#Nude |
|
5 |
Head |
Head |
0 |
#Nude |
|
6 |
Upper Neck |
Neck |
0 |
#Nude |
|
7 |
Lower Abdomen |
Abdomen |
90,30 |
#Briefs + Denim |
|
8 |
Hands |
Hands |
0 |
#Nude |
|
9 |
Upper Arms |
Arms |
5,2 |
#T-Shirt and long sleeve shirt |
|
10 |
Shoulders |
Shoulders |
5,2 |
#T-Shirt and long sleeve shirt |
|
11 |
Upper Abdomen |
Abdomen |
5,2 |
#T-Shirt and long sleeve shirt |
|
12 |
Lower Neck |
Neck |
5,2 |
#T-Shirt and long sleeve shirt |
|
13 |
Lower Arms |
Arms |
2 |
#T-Shirt |
The Human Comfort Module accurately assigns thermal and mass resistances to each layer of clothing and connects it to the skin beneath. While clothing resistances to both heat transfer and diffusion of moisture can be defined by the user, a full library—including over 100 standard articles of clothing—is provided with the license. The human virtual thermal model in this case was assigned an activity level of 1.1, indicating a low level (equivalent to filing papers according to the ASHRAE handbook).
To simulate a transient environment, we seed the Human Comfort Module with a temperature distribution for the body tissues based on an initial conditions state obtained from a previous analysis involving neutral ambient conditions. These initial conditions are imported by the Human Comfort Module at the start of the transient analysis. Because of this change in boundary conditions at the start of the transient analysis, a few time steps may exhibit oscillatory behavior and should be discarded. There are several feedback loops executed in the computation of human comfort, such as blood flow perfusion, arterial dilation/constriction, and shivering/sweating; the first hour of analysis may be discarded as the virtual thermal dummy acclimates to the environment. The transient analysis can also be initiated as a transient restart of a thermally neutral, steady-state environment.
Example Articles of Clothing from the Clothing Database
|
# |
Shirts |
Icl* |
Re,cl* |
fcl* |
|
1 |
Long-sleeve, bow at neck (broadcloth) |
0.786 |
0.0115 |
1.25 |
|
2 |
Long-sleeve, shirt collar (broadcloth) |
0.804 |
0.0119 |
1.235 |
|
3 |
Long-sleeve, shirt collar (flannel) |
1.216 |
0.0235 |
1.235 |
|
4 |
Short-sleeve, shirt collar (broadcloth) |
0.754 |
0.0108 |
1.233 |
|
5 |
Short-sleeve, sport shirt (double knit) |
0.636 |
0.0085 |
1.05 |
Thermal mass and resistances of the human tissues are defined in layers, and again a simple text file is used to define the layering. For example, the head has four layers:
Materials:
|
#Cmprt
|
Layer
|
Matl
|
k
|
density
|
c
|
wbl0
|
qm0
|
r(m)
|
|
Head
|
3
|
Brain
|
0.49
|
1080
|
3850
|
10.132
|
13400
|
0.086
|
|
Head
|
2
|
Bone
|
1.16
|
1500
|
1591
|
0
|
0
|
0.1005
|
|
Head
|
1
|
Fat
|
0.16
|
850
|
2300
|
0.0036
|
58
|
0.102
|
|
Head
|
0
|
Skin
|
0.47
|
1085
|
3680
|
5.48
|
368
|
0.104
|
Results
Animation of Surface Temperatures (avi)
Thermal Sensation (TS)
The plot 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.
Dynamic Thermal Sensation (DTS)
DTS is an extension of the TS value and provides a more accurate prediction of human thermal comfort under rapidly changing transient conditions. Unlike TS (Thermal Sensation), it does consider the time-varying experience of a human exposed to transient thermal conditions. Therefore the history of the human model’s core temperature and body segment temperatures is considered in computing this value. This makes greater intuitive sense as short-term exposure to a warm or cold environment does not produce the same level of dissatisfaction as protracted exposure.
Validation Against 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.
PMV Model inputs:
|
Clothing insulation
|
clo units
|
|
Briefs
|
0.04
|
|
Socks
|
0.02
|
|
Shoes
|
0.10
|
|
Long Sleeve Shirt
|
0.25
|
|
T-shirt
|
0.17
|
|
Trousers
|
0.28
|
|
Metabolic Rate
|
1.1 met
|
|
Work
|
0 met
|
|
Air Temp
|
23C
|
|
Surface Temp
|
21C
|
|
Air Velocity
|
0.15m/s
|
|
Relative Humidity
|
40%
|
|
Total
|
0.86
|
Results of Comparison with the RadTherm/MuSESPro Human Thermal Comfort Module
|
PMV= -0.478
|
RadTherm DTS= -0.54
|
|
PMV PPD=9.78%
|
RadTherm PPD=11.1%
|
Therefore the RadTherm DTS agrees very closely with the steady state PMV value, and the 9.78% of the population dissatisfied predicted by the PMV model agrees very well with the Human Comfort Module PPD value of 11.1%.
The ThermoAnalytics Human Comfort Module is therefore an extremely useful and accurate means of predicting thermal safety (core body temperature) and thermal comfort of humans exposed to realistic, asymmetric transient environmental conditions. Additional validations of the Human Comfort Module have been performed. To further discuss validation or how the Human Comfort Module can benefit your team, contact us for a comprehensive review.
View More Sample Models
This sample model uses thermal design to improve the aircraft’s human comfort while reducing the power load on its climate control system.
This sample demonstrates an evaluation of AC pull-down using two different source air temperature profiles and the resulting effects on localized passenger comfort. The Berkeley Comfort Model provides localized comfort results for each body segment computed from temperatures predicted by our Human Comfort Module.
The analysis for this structure involved a prediction of solar loading as well as air circulation patterns throughout the structure. ThermoAnalytics used RadTherm software to determine the need for transmissive or non transmissive glass and predicted internal temperatures of the Cathedral on a sunny days at both half and maximum occupancy.
A prediction of transient thermal comfort for humans driving a car through the desert. It provides realistic, localized loading of the vehicle's air nodes.
A human thermal model demonstrates the effects of solar intensity and ambient temperature. They drink a cup of coffee as the Human Comfort Module simulates their thermal response to the environment.
RadTherm can predict Formula 1 racetrack surface temperatures. Simulations based on weather and track temperature can be a powerful ally in an event where a racer can win by mere seconds.
We simulated a coil-in-tube cross flow heat exchanger to demonstrate RadTherm's fluid stream and convection heat transfer modeling capabilities. The heat exchanger surfaces were created in Rhino3D and meshed with ANSA. The mesh was exported into RadTherm.
Air travel passengers are all too familiar with the thermal discomforts of summer travel. Our DC-10 model provides insight to thermal management techniques that could improve the experience.
RadTherm can model the thermal behavior of complex systems. In this case, a refrigerated truck transports cargo in a contolled environment. We simulate the vehicle's thermal behavior and the cargo system's thermal response.
One of the most frequent complaints about motorcycles is the engine's heat plume. The plume hits the rider when they're idling in traffic or after getting off the highway. This analysis simulates this heat plume and predicts the temperature increase that the rider will experience.
This sample model demonstrates RadTherm's unique environmental effects applied to architectural analysis. You can generate transient thermal results by combining CFD results with RadTherm.
Thermal simulation of a brake system. The brake model is loosely based on the front rotors of a 2005 Ford Mustang.
This model simulates simple thermostatic control of two heating systems. It represents a common heated plate system used to cure adhesives or control chemical reaction rates.
Modeling the forest canopy generates accurate temperatures or IR signatures of objects in such environments. Studying the canopy can find passive "cool zones" for urban park development. Through simulation, the ideal size and location of trees can be planned to provide improved thermal comfort.
We model the development process of a simple exhaust-shield component model using the supplemental TDFUtility program (supplied with all software from ThermoAnalytics). The TDFUtility is a set of utilities combined into a single executable. We demonstrate how it can improve mesh and model quality.
Sample unmanned ground vehicle signature analysis featuring a simple hybrid drive engine and exhaust system and sensor tower. The defense industry needs to consider the thermal (infrared) signature of its systems under various operating conditions and environments. MuSES performs a full thermal analysis followed by a radiance solution in specific IR wave bands corresponding to the sensor of interest.
The Human Comfort Module is available under a separate license to simulate the thermal response of a human body in an environment with significant thermal loads.
