THERMAL CONDUCTIVITY OF SELECTED ALUMINIUM ROOFING SHEETS IN NIGERIA
Thermal conductivity of six samples was determined. Samples are pure aluminium long span roofing sheets with red, blue, black, green and white colours. Giralle roofing sheet was also examined. The lees’ disc steady state method was used and the results show the thermal conductivity of the samples as follows; 254.609 + 0.0065 Wm-1k-1 for red, 207.253 + 0.0063 Wm-1k-1 for blue, 111.659 + 0.0058 Wm-1k-1 for black, 301.123 + 0.0055 Wm-1k-1green, 229.925 + 0.0053 Wm-1k-1 for white and 152.738 + 0.0055 Wm-1k-1 for giralle respectively. From these results, green coated sheets had the highest thermal conductivity value of 301.123 + 0.0055 Wm-1k-1 and black has the least thermal conductivity value of 111.659 + 0.0058 Wm-1k-1. It was further observed that the colour of coating affected the thermal conductivity of the samples and was therefore concluded that green is the most suitable sample for roofing and black is the least.
TABLE OF CONTENTS
Title Page i
Table of Contents viii
List of Tables xi
List of Figures x
1.0 Introduction 1
1.1 Purpose of the Study 4
1.2 Aim and Objectives of the study 5
1.3 Significance of the study 6
1.4 Scope of the Study 6
REVIEW OF RELATED LITERATURE
2.0 Review of related literature 7
2.1 Temperature gradient 7
2.2 Heat and Internal Energy 9
2.3 Heat transfer mechanisms 10
2.4 Heat flow 10
2.5 Thermal Conductivity (K) 12
2.7 Determination of Thermal Conductivity of a Conductor 17
2.8 Other thermal properties of materials 20
MATERIALS AND METHODS
3.0 Materials and Research Methodology 23
3.1 Materials 23
3.2 Sample Preparation 23
3.3 Sample Analysis 24
3.4 Determination of thermal conductivity (K) of Samples 25
RESULTS, ANALYSIS AND DISCUSSIONS
4.0 Presentation of Experimental Results 30
4.1 Calculations and deductions from graphs or the temperature gradient of Samples 33
4.2 Calculation of thermal conductivity of samples 34
4.3 Discussion of results 36
SUMMARY, CONCLUSION AND RECOMMENDATION
5.0 Summary 38
5.1 Conclusion 39
5.2 Recommendation 40
The topic of heat flow and of course, thermal transport within, a system is a matter of concern to all in the society. Scientists and non- scientists alike especially when it has to do with the basic needs of life; food, shelter and clothing.
Thermal conduction and heat transfer is basically governed by thermal conductivity of the materials that make up a system. Heating process involves basically a transfer of thermal energy from one region to another (Etuk, Akpabio & Akpabio 2005). This transfer can take place in three ways namely; conduction, radiation and convection. It is therefore worthy of brief discussion for the purpose of completeness and refreshing the memory, the three primary methods of heat transmission earlier mentioned
In convection, heat is carried from one place to another by a physical agent such as fliud (liquid or gas). Conduction involves thermal agitation of molecules passed throughout a substance. In conduction, the average position of molecules remain the same, but not so with convection, though the two require material medium such as solid, liquid or gas for heat transmission, whereas, no material substance is required in the case of radiation, being wavelike mode of heat transfer in which heat is treated as electromagnetic waves.
Thermal conduction is therefore a transport of heat energy from the warmer part to the colder part of the same body or from the warmer to the colder body in physical contact with each other without displacement of the particles of the body.
Thermal conductivity, specific heat capacity and thermal diffusitivity are seen as the major important properties of materials, but thermal conductivity is particularly an important parameter to manufacturing devices expressing the relationship between the parameters thus;
is the thermal conductivity of the material,
is the density of the material,
d is the thermal diffusitivity and
c is specific heat capacity
According to Ababio (2003), aluminium is the third most plentiful element in the earth’s crust, being found abundantly as trioxosilicates (IV) in rocks and clays. The main source of aluminium is the mineral bauxite. Bauxite can be converted to aluminium oxide (alumina) through the Bayer process. The alumina is then converted to aluminium metal using electrolytic cells and the Hall – Heroult process. Its versatility makes it the most widely used metal after steel.
Aluminuim is an execellent reflector of raiant energy, from ultraviolet to infrared. It has a visible light reflectivity of around 80%, which makes it widely used in light fixtures. It is its high reflectivity to visible light that makes aluminium roofing sheets come in various aesthetic patterns and colours.
By exploiting combinations of its physical properties such as strength, lightness, corrosion resistance, recyclability and formidability, aluminium is being employed in an ever increasing number of applications. This array of products ranges from structural materials, roofing sheets through to thin packaging foils. It is also widely used in the manufacture of cooking utensils owing to its non-toxic nature and high conductivity.
This work is designed to investigate the thermal conductivity (k) of roofing sheets made from aluminium and coated red, blue, green, black, white and giralle.
- PURPOSE OF THE STUDY
The purpose of this work is to determine the thermal conductivity of aluminium roofing sheets coated red, blue, black and white, and of giralle pigments and use these values to determine whether or not the thermal conductivity is affected by the colour of coating.
Furthermore, appropriate recommendations as to which colour is suitable for roofing will be made from the results.
- AIMS AND OBJECTIVES OF STUDY
The aim of this work is to determine the thermal conductivity of aluminium roofing sheets coated with red, blue, black and white. Giralle roofing sheet will also be examined.
The specific objectives are;
- To determine the thermal conductivity of the samples.
- To determine which colour of coating is more suitable for roofing based on the thermal conductivity values.
- To ascertain if the colour of coating has effect on the thermal conductivity of the samples.
- SIGNIFICANCE OF STUDY
This work is immensely important to the domestic and industrial setting. Amongst others, it will help determine the temperature comfortability of buildings with respect to the colour of coating of roofing sheets based on their thermal conductivity values.
- SCOPE OF STUDY
This work is limited to;
- Aluminium roofing sheets coated red, blue, green, black and white and having a thickness of 0.50mm.
- Giralle roofing sheet coated black.
- Only thermal conductivity of the samples are investigated. Other thermal properties are not considered.