Indian Institute of Technology Gandhinagar

CL 351 HEAT AND THERMODYNAMICS LAB

Final Project Report

Group Members

Dablu Kumar 20110049

Rahul Kumar 20110153

Manish Jangir 20110107

Amit Kumar 18110019

Index 1
Introduction 2
Acknowledgement 3
Objective 4
Schematic diagram of the Setup 5
Theory
Theoritical Analysis 6
Heat principal
Heat gain
Heat loss
Conduction
Convection
Radiation
Reflection of light
Design of Experiment Setup 7

Experimental Procedure 8
Required Material
Procedure
Precaution
Results And Discussion 9
Observation 10
Conclusion 11
Future Work 12
Remarks 13
Reference 14

1
Inroduction
The global population is increasing rapidly, so food, energy, and water consumption are also growing. As of
now, the global population is using approx. 80-85% of the total energy comes from non-renewable resources.
However, fossil fuels are limited; they cannot be replaced if these resources are used. So, we should try to
use renewable resources as much as possible to preserve them for the future.

In recent years, it has been seen that many countries have already started the use of renewable
resources for their daily use purposes. One of the famous examples is the use of solar cells for electricity
production. Therefore, in today's world, the use of solar energy has risen, especially with the increasing fuel
costs and the efforts to reduce greenhouse gas emissions. The invention of the solar oven has provided an
opportunity to be environmentally friendly, to cook a wide variety of food using the power of the Sun as the
device's heat source. For many worldwide countries with limited access to clean water, the solar oven also
offers a solution by sterilizing the water. It is also helpful for travelers to cook food in mountain areas, as the
solar oven can be made as portable as possible.

Acknowledgment
We want to express special gratitude to our Heat and Thermodynamics Lab professor, Prof. Biswajit Saha,
for giving us a golden opportunity to do this wonderful project on the real-world application of the heat
transfer and thermodynamics course.

We extend our gratitude to IIT Gandhinagar for providing us with all the required facilities. Secondly, We
would like to thank Supresh Sir, who helped us get the necessary equipment and finish the project. Thanks to
all who helped us in completing the project.

Objective
The project's purpose is to design an efficient solar oven that is easily accessible. Many villages all over the
world have no access to electricity. In this case, people can use the solar oven that only requires energy from
the sun that is renewable and readily available. Some people cannot afford the price of a solar oven, so it
must be affordable.

OUR MAJOR OBJECTIVES ARE THE FOLLOWING:

● To develop a new design of solar oven

● Should be affordable
● Design must be compact and efficient using the sunlight
● Compare the temperature inside and outside of the cooking chamber

2
Schematic diagram of the Setup
The solar oven should provide high-temperature gain, a large area to incubate oversized utensils to cook
food, and it should be easy to carry. The oven can be divided into two sections one reflects sunlight, and the
other is a box to retain the sunlight and convert it into heat energy.

To reflect sunlight, smooth aluminum foil or aluminum sheets are used. These sheets are fixed on cardboards
of the same size to get support. Four such sheets are used, and all of these are bound at the edge of each other
(inclined angles analysis can be seen in the above theoretical analysis part) using adhesive materials to reflect
sunlight properly in the box as the sun moves. These sheets can be unbound to carry the heater at any place.

The box where the sunlight is reflected is a light wooden box whose outer sides are made of laminated
wooden sheets. Inside the box, black foam is placed in contact with the wooden sheets to provide proper
insulation. On the base of the box, black paper sheets are used. A glass plate of size equal to the opening of
the box is also required to provide heat to the greenhouse effect and to reduce heat loss.

For cooking inside a solar oven, black iron core ceramic pots are preferred as they absorb the heat readily and
make the cooking easy.

Schematic diagram of the device

Theory
The majority of the time, reflecting panels, petals, and other surfaces that can "focus" or concentrate UV light
rays to a point or concentration are used to concentrate the sun's rays. These reflecting panels are typically
made of shiny, reflective materials like silver, chromium, and aluminium because of the materials utilised in
their production. Most solar cookers are built with reflector panels to speed up the process of heat buildup
since without a way to focus the sun's rays, it can take longer to heat objects or surfaces.

Absorption of the sun's energy (heat)in solar cooking is best achieved when a surface is dark in color, thus
the most common solar oven interiors are usually black in color as well as the color of the cookware used for
cooking the food.

3
Dark colors absorb the heat, whereas light colors do not absorb heat well. And some colors can reflect the
sun's energy away, such as silver for example. Generally, the best cookware for solar cooking is the dark, thin
variety because it absorbs the heat (energy) well; and because it is thin, it can then transfer the heat more
quickly and evenly to the food.

The last solar cooking principle is retention. All of the concentrated heat (energy) and all of the absorbed
heat would soon disperse into the air and be lost to the surroundings if a solar cooker is poorly insulated and
does not have a cover or lid. A solar cooker needs to be able to "trap" or hold the focused heat so that it can
build up and accumulate to high enough levels to be able to cook.

A fourth principle is: transparency of your retentive materials, which means that your lid on a solar oven or
your enclosure around your pot or pan on a solar panel cooker needs to be able to allow the sun's rays to
penetrate inside to where the food or cooking vessels are located. Parabolic cooking is one form of solar
cooking that uses this principle. The lid, door, or enclosure of a solar cooker is typically covered with clear
glass or plastic to allow the sun's rays to pass through while also acting as an inhibitor and trapping heat.

Theoretical Analysis
● Heat exchange between the glass and the outside environment
Heat exchange will only happen due to radiation and convection.

𝑄𝑒𝑛𝑣 = (ℎ𝑐,𝑎𝑚 + ℎ𝑟, 𝑣−𝑠𝑘𝑦) * (𝑇𝑣 − 𝑇𝑎𝑚)

Where: ℎ𝑐,𝑎𝑚 : Coefficient of exchange by convection between the glass and the ambient

ℎ𝑐,𝑣−𝑠𝑘𝑦: radiation echange coefficent between the glass and sky

𝑇𝑣 : Tempreture pf the window (K)

𝑇𝑎𝑚: Ambient temperature

ℎ𝑐,𝑣−𝑠𝑘𝑦 = 5. 67 + 3. 86𝑉𝑤𝑖𝑛𝑑𝑉𝑤𝑖𝑛𝑑(𝑤𝑖𝑛𝑑 𝑠𝑝𝑒𝑒𝑑) < 5𝑚/𝑠

4 4
σε𝑣(𝑇 −𝑇 )
𝑠𝑘𝑦
ℎ𝑐,𝑣−𝑠𝑘𝑦 = 𝑇𝑣−𝑇𝑎𝑚

Where: σε𝑣: Boltzman constant

ε𝑣: glass emissivity

1.5
𝑇𝑠𝑘𝑦 = 0. 552𝑇 𝑎𝑚

4
So now the equation
4 4
𝑄𝑝,𝑎𝑣1 = ℎ𝑐,𝑣−𝑎(𝑇𝑣 − 𝑇𝑎𝑚) + σε𝑣(𝑇 𝑣
−𝑇 )
𝑠𝑘𝑦

● Heat Exchange between the glass and the absorber

Teh heat exchange between the glass and the observer plate is by convection and radiation.
𝑄𝑔−𝑎 = (ℎ𝑐, 𝑔−𝑎 + ℎ𝑟, 𝑔−𝑎)(𝑇𝑎+𝑇𝑔)

ℎ𝑐, 𝑔−𝑎: Coefficient of heat transfer by convection between the glass and the absorber and

ℎ𝑟, 𝑔−𝑎 : coefficient of heat transfer by radiation between the glass and the absorber given by:

2 2
σ(𝑇𝑎+𝑇𝑎)(𝑇𝑎 +𝑇𝑎 )
ℎ𝑟, 𝑔−𝑎 = 1 1
ε𝑔
+ ε −1
𝑎

where:

𝑇𝑎 : Absorber temperature

𝑇𝑔: Glass temperature

ε𝑔 :Emissivity of the glass

ε𝑎 : Emissivity of the absorber

● Heat principal
Box solar oven is a device that heats up the things inside the box. Because the sun's energy heats the box's
interior, a solar box can cook. Through the glass or plastic top, sunlight enters the solar box and is reflected.
When absorbed by the black absorber plate and cooking pots, it transforms into heat energy.
In any heating process, three phenomena happen heat gain, heat loss, and heat storage.

● Heat gain
In the solar oven heater, heat is gained by the greenhouse effect phenomena. This phenomenon causes
enclosed spaces where the light shines through a transparent material, such as glass, to heat up. Visible light
is easily transmitted through the glass and is absorbed and reflected by the interior components.

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Once light enters the heating chamber through glass, this is absorbed by the black paint or dark absorber
plate and converted into longer wavelength heat energy. Because of its longer wavelength, it connotes
passing back out through the glass and is trapped within the oven box.

● Heat loss
According to the second law of thermodynamics, heat flows from higher to lower temperatures. So, in our
case, also inside the oven box, the temperature is more than the ambient. Therefore, heat will flow from the
oven box to the ambient, called heat loss. In the solar oven, heat loss occurs through conduction, convection,
and radiation.

● Conduction
Conduction happens through the wall of the box. Therefore, we insulate the oven box wall to reduce heat
loss.

∆𝑇
𝑄 = − 𝐾𝐴 𝐿
Where:
𝑄 = ℎ𝑒𝑎𝑡 𝑡𝑟𝑎𝑛𝑠𝑓𝑒𝑟
𝐾 = 𝑇ℎ𝑒𝑟𝑚𝑎𝑙 𝑐𝑜𝑛𝑑𝑢𝑐𝑡𝑖𝑣𝑖𝑡𝑦 𝑜𝑓 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙
𝐴 = 𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑏𝑦 𝑤ℎ𝑖𝑐ℎ ℎ𝑒𝑎𝑡 𝑖𝑠 𝑡𝑟𝑎𝑛𝑠𝑓𝑒𝑟𝑖𝑛𝑔
∆𝑇 = 𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒
𝐿 = 𝑤𝑖𝑑𝑡ℎ 𝑏𝑦 𝑤ℎ𝑖𝑐ℎ ℎ𝑒𝑎𝑡 𝑖𝑠 𝑡𝑟𝑎𝑛𝑠𝑓𝑒𝑟𝑖𝑛𝑔

● Convection
Molecules of air move through the cracks in and out of the box. This results in convective heat transfer.
Heated molecules within the solar box escape, primarily through the cracks and any other leakage in the solar
box.

6
 𝑄 = − ℎ𝐴(∆𝑇)

Where:
𝑄 = ℎ𝑒𝑎𝑡 𝑡𝑟𝑎𝑛𝑠𝑓𝑒𝑟
ℎ = 𝑐𝑜𝑛𝑣𝑒𝑐𝑡𝑖𝑣𝑒 ℎ𝑒𝑎𝑡 𝑡𝑟𝑎𝑛𝑠𝑓𝑒𝑟 𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡
𝐴 = 𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑏𝑦 𝑤ℎ𝑖𝑐ℎ ℎ𝑒𝑎𝑡 𝑖𝑠 𝑡𝑟𝑎𝑛𝑠𝑓𝑒𝑟𝑖𝑛𝑔
∆𝑇 = 𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒

● Radiation
The thing that we want to warm or cook. When the material inside the solar box is heated, it produces heat
waves. These heat waves radiated from the warm objects through air space. Most of the radiated heat is given
off by the warm wall and the glass back to the surroundings. However, the glass resists most of the heat
waves. The heat loss through the radiation is less than the conduction and convection.

4 4
𝑃 = ε * σ * 𝐴(𝑇 2
− 𝑇 1)
Where:
𝑃 = 𝑃𝑜𝑤𝑒𝑟 𝑑𝑖𝑠𝑠𝑖𝑝𝑎𝑡𝑒𝑑 𝑡ℎ𝑟𝑜𝑢𝑔ℎ 𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛
ε = 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑒𝑚𝑚𝑖𝑠𝑠𝑖𝑣𝑖𝑡𝑦 𝑜𝑓 𝑡ℎ𝑒 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙
σ = 𝑆𝑢𝑟𝑓𝑎𝑐𝑒 − 𝐵𝑜𝑙𝑡𝑧𝑚𝑎𝑛 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 𝑎𝑟𝑒𝑎 𝑏
𝐴 = 𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑝𝑎𝑐𝑘𝑎𝑔𝑒
𝑇1 = 𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑜𝑓 𝑝𝑎𝑐𝑘𝑎𝑔𝑒
𝑇2 = 𝐴𝑚𝑏𝑖𝑒𝑛𝑡 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒

● Reflection of light
Reflection of light is referred to as light reflection when a light ray hits a polished, smooth surface and
bounces back. The incident light rays hit the surface and are reflected off of it. The beam that returns is
referred to as the reflected ray.
Here, i = r, i.e., the angle of incidence is equal to the angle of reflection.

There are two scenarios based on sunlight:-

1. When the sunlight is coming straight to the reflectors.
2. When the sunlight is coming at an inclination to the reflectors.

7
The temperature of the oven heater depends upon the area of reflectors on which sunlight falls. This area is
defined as a capturing area. The more area is captured, the more sunlight falls on the reflectors, resulting in
more heat.

The captured area is dependent upon the length and angle of the reflector.

We have to also take care of the angle of reflection, which means we can increase the reflector length and
angle for a fixed base area of the heating chamber.

8
So for the particular targeted area and length of reflectors, we have to find the angle at which we have to fix
the reflector.

Here is a formula to find the inner and outer angel of reflectors

𝑖𝑛𝑛𝑒𝑟 𝑎𝑛𝑔𝑙𝑒 = 90 + 𝑠𝑖𝑛

𝑜
(
−1 − 𝑅𝑒𝑓𝑙𝑒𝑐𝑡𝑜𝑟 𝑙𝑒𝑛𝑔ℎ𝑡
4 * 𝑡𝑎𝑟𝑔𝑒𝑡 𝑤𝑖𝑑𝑡ℎ
+
1
4
𝑅𝑒𝑓𝑙𝑒𝑐𝑡𝑜𝑟 𝑙𝑒𝑛𝑔ℎ𝑡
𝑡𝑎𝑟𝑔𝑒𝑡 𝑤𝑖𝑑𝑡ℎ
+ 8 )
𝑜
𝑜𝑢𝑡𝑒𝑟 𝑎𝑛𝑔𝑙𝑒 = 180 − 𝑖𝑛𝑛𝑒𝑟 𝑎𝑛𝑔𝑙𝑒

𝑣𝑒𝑟𝑡𝑖𝑐𝑎𝑙 ℎ𝑒𝑖𝑔ℎ𝑡 = 𝑠𝑖𝑛(𝑜𝑢𝑡𝑒𝑟 𝑎𝑛𝑔𝑙𝑒) * 𝑟𝑒𝑓𝑙𝑒𝑐𝑡𝑜𝑟 𝑙𝑒𝑛𝑔𝑡ℎ

Design of Experimental Setup

Here we discuss how the angle, length, width of the designed setup has been calculated.

First of all, we found the formula to find the inner angle of the reflectors from the literature survey

Only we have to fix the reflector length and the target width to find the inner angle.

𝑖𝑛𝑛𝑒𝑟 𝑎𝑛𝑔𝑙𝑒 = 90 + 𝑠𝑖𝑛

𝑜
(
−1 − 𝑅𝑒𝑓𝑙𝑒𝑐𝑡𝑜𝑟 𝑙𝑒𝑛𝑔ℎ𝑡
4 * 𝑡𝑎𝑟𝑔𝑒𝑡 𝑤𝑖𝑑𝑡ℎ
+
1
4
𝑅𝑒𝑓𝑙𝑒𝑐𝑡𝑜𝑟 𝑙𝑒𝑛𝑔ℎ𝑡
𝑡𝑎𝑟𝑔𝑒𝑡 𝑤𝑖𝑑𝑡ℎ
+ 8 )
Here,
Reflector length = 25 cm
Target width = 35 cm

Now, if we put both the values in the above equations, we get

𝑖𝑛𝑛𝑒𝑟 𝑎𝑛𝑔𝑙𝑒 = 90 + 𝑠𝑖𝑛

𝑜
(
−1 − 𝑅𝑒𝑓𝑙𝑒𝑐𝑡𝑜𝑟 𝑙𝑒𝑛𝑔ℎ𝑡
4 * 𝑡𝑎𝑟𝑔𝑒𝑡 𝑤𝑖𝑑𝑡ℎ
+
1
4
𝑅𝑒𝑓𝑙𝑒𝑐𝑡𝑜𝑟 𝑙𝑒𝑛𝑔ℎ𝑡
𝑡𝑎𝑟𝑔𝑒𝑡 𝑤𝑖𝑑𝑡ℎ
+ 8 )
9
 𝑜 −1
𝑖𝑛𝑛𝑒𝑟 𝑎𝑛𝑔𝑙𝑒 = 90 + 𝑠𝑖𝑛 (0. 5594)

𝑜
𝑖𝑛𝑛𝑒𝑟 𝑎𝑛𝑔𝑙𝑒 = 90 + 34. 01

𝑜
𝑖𝑛𝑛𝑒𝑟 𝑎𝑛𝑔𝑙𝑒 = 124

𝑜 𝑜 𝑜
𝑜𝑢𝑡𝑒𝑟 𝑎𝑛𝑔𝑙𝑒 = 180 − 124 = 56

Engineering Diagram of the setup

Setup just after completed Setup kept at hostel Terrace in sunlight

10
Experiment Procedure
● Required material:
● Glass
● Cardboard
● Black paint
● Aluminum foil/sheet
● Three Thermo-meter
● Insulating materials (foam)
● Adhesive materials (glue, tape)
● Procedure:

1. First we took a cardboard box of size 34 cm x 34 cm

2. The insulation foam was sticked to all the 4 walls of the cardboard

3. Besides the insulation foam, we again added the cardboard walls of the same dimensions.

4. Base area and the inner card walls are painted with black paint

5. Then we extended the area of the side walls to make the reflectors

6. The aluminium foil was stikked to the reflectors.

7. At last, put the transparent glass over the foam.

Our setup was completed and it was ready for experiment.

● Precaution:
● The solar oven is used for cooking food, so the temperature inside the oven will be high enough to
cause serious burns.
● Sunlight is directly reflected from the aluminum sheet, so use the goggles during the experiment.
● We have to take care of weather conditions because the oven needs direct sunlight to work properly,
so if we use it on rainy or cloudy days, its efficiency will decrease.
● For now, we have set oven design material on cardboard, so take it away from water.

11
 ● Mostly, sunlight is more effective from 10:00AM to 2:00 PM, so scheduling our experiment during
this period will be great.
● We often use knives to cut the cardboard, so be careful during cutting.

Results And Discussion

The setup is put into sunlight in the afternoon and the inside temperature reading is taken by a thermometer
inserted through the wall of the solar heater oven. The temperature increases rapidly with time and reaches a
maximum temperature after 1.5 hour.

Table of experimental data of temperature with time

Time (min) Temperature (degree celcius) Ambient Temperature

0 28 28

10 38 29
20 50 30
30 70 31
40 75 32
50 80 32.5
60 85 33
70 88 33.5
80 88.8 34
90 88 34.5
100 87 35

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Observation
The temperature of the solar oven heater is expected to reach 125℃ from 11 am to 3 pm, which will be
sufficient to pasteurize water and cook traditional foods like rice. Using the oven on cloudy days is
challenging as the generated interior temperature will be low.

Conclusion
Traditionally, cooking is done with solid fuels like wood, crop waste, coal, or LPG. These sources are
depleting daily, and burning them releases harmful gases. Oven solar heaters work on sunlight, which is
renewable energy, and produces no toxic gas that can harm the environment. In this experiment, we reflect
and concentrate sunlight inside an insulated box. The sunlight gets converted into longer wavelength infrared
light rays, which cannot escape through the glass put on the opening of the box. These light rays produce
heat energy which cooks the food item put inside.

● We have successfully completed the setup and did the experiment.

● The Inside temperature was increasing continuously with increasing time.
● Ambient temperature was also increasing but not as fastly as the inside temperature. It is increasing
𝑜
gradually upto 90 𝐶
𝑜
● Maximum inside temperature was reached upto 88. 8 𝐶

13
Future work
● Although the current solar oven technology helps cook food, its efficiency can be increased so that
the time required to cook decreases. More layers of insulation can be put in to lower the heat loss.
● One major drawback of a solar oven is that it can’t be used in presence of lower sunlight or in case of
no sunlight. Using thermal energy storage(TES) can overcome these problems. Phase change
materials(PCM) can be used as TES to increase the performance of solar oven heaters. A PCM which
can change the phase between solid-liquid in required temperature range of cooking is suitable for
this solar heater.

Remarks
● Challenges
○ The temperature measurement device was not working properly.
○ If we would have two temperature sensors, it would be better for measuring the data
for inside and ambient temperature both. We have only one device.
● Solutions
○ We can buy better temperature measurement devices that are also compatible with the
higher temperature.
○ We can buy two devices for easy measurement.

Reference
1. https://leverageedublog.s3.ap-south-1.amazonaws.com/blog/wp-content/uploads/2020/
04/16224940/Reflection-Of-Light-1-1024x640.png
2. https://static.wikia.nocookie.net/solarcooking/images/2/2c/Box_Cooker_Principles
_Figure_02.gif/revision/latest?cb=20080513064408
3. https://solarcooking.fandom.com/wiki/Health_and_safety#Important_considerations_w
hen_solar_cooking
4. https://www.education.com/science-fair/article/design-solar-cooker/
5. https://solarcooking.fandom.com/wiki/Principles_of_Solar_Box_Cooker_Design
6. https://www.elprocus.com/steps-to-make-solar-cooker/
7. https://www.idt.com/sites/default/files/useruploads/knowledgebase_images/radiation_e
quation.png
8. https://www.solarcooker-at-cantinawest.com/solarcooking-howitworks.html

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