2026-09-22T10:04:26Zhttps://dora.dmu.ac.uk/server/oai/requestoai:dora.dmu.ac.uk:2086/132692019-03-20T03:58:38Zcom_2086_2388col_2086_2389
Asymmetric radiant fields and human thermal comfort
Kubaha, Kuskana
The main purpose of this thesis was to develop a first principles model for
predicting human local thermal comfort responses to asymmetric radiation
environments. The research deployed state-of-the-art computer simulation
techniques to model in detail inhomogeneous short-wave and long-wave
radiative heat exchanges of standing and sedentary humans. Detailed 3D
human geometry models, simulation software incorporating advanced, voxelbased
ray techniques and statistical regression analysis were used to accurately
model human local geometry-related characteristics, i.e. projected area factors
with respect to both direct and diffuse solar radiation, and view factors for
individual parts of the human body.
The local projected area factors with respect to direct short-wave radiation
(fp,dir) were presented as functions of the solar azimuth angle (a) between 0 0<
a < 3600 and the solar altitude (jJ) angles between -900 <fi<+90o. In case of
diffuse solar radiation from the isotropic sky the local human projected area
factors (fp,dij) were modelled as a function of the ground albedo (pg) ranging
between 0< pg <1. The functions were validated against available experimental
data and showed good general agreement with projected area factors measured
for both the human body as a whole and for local quantities.
The view factors of individual body parts were modelled as functions of local
projected area factors. This technique makes it possible to predict view factors
between individual body parts and surrounding surfaces for almost any
arbitrary geometrical configurations. ?Validation showed good agreement with
available experimental data for both standing and sedentary humans.
The detailed projected area factors and view factors developed were used in
conjunction with the IESD-Fiala multi-node model of human heat transfer and
thermal comfort to predict thermal responses of subjects exposed to various
asymmetric radiation conditions. The extended model showed good agreement
with available measured data obtained for frontal, lateral, horizontal and
vertical thermal radiation asymmetries as well as for direct solar radiation.
A new comfort model was developed using physiological parameters which
predicts human local responses to asymmetric radiation in terms of percentage
of dissatisfied due to local discomfort. Both local cold discomfort (LCD) and
local warm discomfort (LWD) which are based on different physiological
principles - were modelled as two separate responses. LCD was found to be a
function of the sensitivity-weighted local skin temperature as related to the
actual general thermal state of the human body described by the mean skin
temperature. LWD was modelled as an exclusive function of local influences, i.e.
the (sensitivity-weighted) local skin temperatures and the corresponding local
setpoint values (referring to skin temperatures in a thermo-neutral environment
of 30?C). The new model was verified and validated using various experiments
in which the subjects were exposed to different types of asymmetric radiation
conditions. The test showed good/acceptable level of agreement with measured
data regarding the percentage of dissatisfied due to local discomfort, the
location on the body where discomfort was perceived, as well as the dynamics of
the local response (Le. time dependence).
The new comfort model was linked with a building simulation program to
predict thermal comfort conditions in buildings. A computational procedure
was developed to enable this in conjunction with ESP-r which is one of the most
well known building simulation programs. The new link enables researchers to
perform detailed thermal comfort analysis and occupant implications of the
dynamic climate conditions in buildings with daily, monthly, seasonal and
annual statistics, and facilitates to quantify the thermal comfort implications of
different building designs and individual constructions.
De Montfort University
2005
Thesis or dissertation
Doctoral
PhD
en
http://hdl.handle.net/2086/13269
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