Page 98 - rise 2017

Problem Statement
Currently, there is no effective type of hot air extractors that specially designed for various cars in the
market. The available portable heat extractors in market are installed to the side window of car and
using solar power to rotate the fan. Due to their dependence on the sun, solar car ventilators do have a
few weak points:-
i. They often need direct sunlight to function, so they may not work on hot but cloudy days.
ii. Manufacturers warn that the devices are still increase the temperature in the cabin in a sunny
day.
iii. Solar ventilators require user to crack open their car window, which could conceivably invite
thieves to attempt breaking into the car.

The design of the heat extractor has to consider the whole range of heat flow in a closed
boundary in order to provide a complete view of its performance. The existing heat extractors are
usually not properly refined and optimized to enable high flow rate of heat from interior of the car. In
addition, the efficiency of the current heat extractor design is also an issue as it is designed for
simplicity which will contribute to lack in efficient heat flow performance. Owners of solar car
ventilators have frequently complained that the devices do not work if it panel is facing away from
direct sunlight. In fact, parking in the shade or even with the solar panel facing away from the sun can
render solar vents useless. We also have conducted an experiment for the existing ventilation product
and the result that we get is not very satisfying.

Objectives
The specific objectives of the proposed study are as follows:
a) To develop a new prototype of hot air extractor for vehicle cabin to improve the existing
product with an appropriate modifications.
b) To investigate the heat transfer flow between the vehicle cabin and the environment under
direct sunlight condition with and without the ventilations.
c) To compare the performance between the existing hot air extractor with our designed hot air
extractor.
d) To study and provide other important features that can be used to improve our designed hot
air extractor.

Literature Review
The greenhouse effect is a naturally occurring process that caused rise in temperature that the earth
experiences because of certain gases in the atmosphere such as water vapour, carbon dioxide, nitrous
oxide, and methane trap the energy from the sun by absorbing long wave radiation emitted from the
earth's surface. Hence, without these gases the heat generated can escape back into the space and as a
result, the earth’s average temperature would be about 60°F colder (United States Environmental
Protection Agency, 2006). Due to this reason, these gases are referred to as greenhouse gases.
As energy from the sun passes through the atmosphere a number of things take place. A
portion of the energy which about 26% globally is reflected or scattered back to space by clouds and
other atmospheric particles. About 19% of the energy available is absorbed by clouds, gases (like
ozone), and particles in the atmosphere. Of the remaining 55% of the solar energy passing through the
earth's atmosphere, 4% is reflected from the surface back to space. On average, about 51% of the sun's
radiation reaches the surface (Pidwirny, 2006). This energy is then consumed in a number of
processes such as the heating of the ground surface, the melting of ice and snow, the evaporation of
water and also the development of plant photosynthesis.
The heating of the ground by sunlight has made the earth's surface to become a radiator of
energy in the long wave band or in other word infrared radiation. Usually, this emission of energy is
directed to a space. Nevertheless, only a small portion of this energy actually makes it back to space
and the remaining of it will be absorbed by the greenhouse gases.
Basically, the greenhouse effect is important. Without this effect, the earth would not be
warm enough for humans to live. However, if the situation becomes stronger, it will turn the earth to
become warmer than usual. Consequently, this extra warming may give serious problems for humans,