The original IESD-FIALA model was developed in 1998 by Dr Dusan Fiala to predict human thermal responses and the associated thermal sensation in a wide range of environments. The model enables thermal influences on human beings to be analysed for transient and heterogeneous conditions with respect to both environmental influences and varying activity levels. The corresponding computer program of the IESD-FIALA model was written in PASCAL, and compiled to run on Microsoft DOS/WINDOWS® platforms (including Windows XP and Vista).
Detailed human model
Computer simulation of the human thermoregulatory system has been a valuable research tool contributing to a deeper understanding of the principles of human thermoregulation. Besides physiological research, there is a growing interest to predict human physiological and comfort responses also in other disciplines of science and technology.
A mathematical model of human thermoregulation and thermal comfort has been developed at IESD, De Montfort University Leicester, based on more than ten year’s research work. The multi-node, dynamic model incorporates two interacting systems of thermoregulation: the controlling, active system and the controlled passive system.
The passive system (Fiala et al. 1999) is a multi-segmental, multi-layered representation of the human body with spatial subdivisions which includes a detailed representation of the anatomic, thermophysical and thermophysiological properties of the human body. The model accounts for phenomena of human heat transfer that occur inside the body (blood circulation, metabolic heat-generation, -conduction, and -accumulation) and at its surface (free and forced surface convection, long- and shortwave radiation, skin moisture -evaporation, -diffusion, and -accumulation).
The active system model (Fiala et al. 2001) simulates responses of the human thermoregulatory system, i.e. suppression (vasoconstriction) and elevation (vasodilatation) of the cutaneous blood flow, sweat moisture excretion and changes in the metabolic heat production by shivering thermogenesis. The active system was developed by means of regression analysis using measured responses obtained from steady and transient exposures to cold stress, cold, moderate, warm and hot stress conditions, and exercise intensities between 0.8 - 10 met.
The simulation system incorporates a dynamic thermal comfort model which predicts human perceptual responses from physiological states of the body. The comfort model has been derived by regression analysis using measured thermal sensation votes obtained from over 2000 male and female subjects.
The thermoregulatory and comfort models have been validated extensively against independent experimental data and showed good agreement with measured regulatory responses, mean and local skin temperatures, internal temperatures and thermal sensation responses for the whole spectrum of environmental conditions investigated and for different personal circumstances (Fiala et al. 2001, 2003).
Scientists and engineers can use the model to study responses of (unacclimatized) humans to a wide range of boundary conditions. The IESD-Fiala model provides a basis for a detailed analysis of the transient and complex inhomogeneous environments found in cars, buildings and other man-made spaces and for the analysis of outdoor weather conditions.
The model has found applications, e.g. in medical engineering to predict temperature and regulatory responses of anaesthetised patients, in the car industry to predict passengers' responses to the transient and asymmetric boundary conditions found inside car cabins, in meteorology to quantify human physiological and comfort responses to outdoor weather conditions, some military applications, and the thermal comfort analysis of buildings and individual built components.
How to get it
The original IESD-Fiala model is copyrighted by De Montfort University. It is provided free of charge for non-commercial use. To obtain a copy, please download the user agreement form (22.26 KiB, 0 downloads), read, sign and date before send it back by post, or a scanned copy by email, to Dr Yi Zhang. A password will then be provided for accessing the download page below. Please note that postgraduate students should ask their supervisors to sign the form.
Download IESD-Fiala model (login is required)
As an alternative, I am considering to release a Java version (jFiala) of the Fiala model. jFiala was a porting of the original IESD-Fiala model so that it can run on multiple platforms. Over the years, improvements have been added to make it a better framework for customizing/developing human thermal models. The drawback, however, is that jFiala is no longer guaranteed to produce same results as the original IESD-Fiala model. We are in the process of validating jFiala. A comprehensive comparison between jFiala and IESD-Fiala will be provided in due course.
Some of the new features of jFiala are:
- Exposing model parameters of human body for developing individual models
- Exposing thermal regulatory models and parameters for calibrating the active system
- Revised solver iteration control to improve numerical stability
- Additional pre-conditioning settings to allow core temperature and mean skin temperature being set at the start of the experiment
- Improved output options and format
If you want to try jFiala, please leave a note using the discussion board below. I will make a copy available on this page if there is enough interest. – Yi, 3 May 2012
Fiala D., K.J. Lomas, and M. Stohrer (1999) A computer model of human thermoregulation for a wide range of environmental conditions: The passive system. Journal of Applied Physiology, Vol. 87 (5), pp. 1957-1972.
Fiala D., K.J. Lomas, and M. Stohrer (2001) Computer prediction of human thermoregulatory and temperature responses to a wide range of environmental conditions. International Journal of Biometeorology, Vol. 45, pp. 143-159.
Fiala D., K.J. Lomas, and M. Stohrer (2003) First Principles Modelling of Thermal Sensation Responses in Steady State and Transient Boundary Conditions. ASHRAE Transactions, Vol. 109 (1), pp.179-186.
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