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Investigation of the thermal performance of coconut fibre composite with aluminium reflector cooling roofs

Abstract

Global warming and depletion of petroleum resources have made the scientists to focus on new passive cooling techniques to reduce the indoor temperature of residential and commercial buildings. This paper explores the benefits of using coconut fibre composite as a passive cooling roof and quantifies those benefits in terms of heat flow changes through field experiment and compares them to the base case of standard roof in arid regions. The research also focussed on the usage of this material in combination with radiation reflectors such as aluminium and the effect of air gap between coconut fibre composite and aluminium reflector on the energy efficiency of the buildings. Experimental investigation showed a substantial reduction in room air and concrete roof slab temperature of coconut fibre composite with aluminium reflector room in comparison with the conventional roof. A maximum reduction of 5.99 °C (16.59%) and 8.39 °C (23.8%) were observed in room air and roof slab temperature of coconut fibre composite–aluminium roof with an air gap of 40 cm between them. It was also observed that as the air gap between coconut fibre composite and aluminium reflector is increased, the room air and roof slab temperature were reduced due to enhanced convective cooling. Compared to a standard roof, the indoor air temperature of coconut fibre composite roof was reduced by a maximum of 2.2 °C (5.86%), 2.9 °C and 5.99 °C (16.59%) for 0, 20 and 40 cm air gap between the coconut fibre composite and aluminium reflector, respectively. It is convincingly demonstrated that the coconut fibre composite roof with aluminium reflector can significantly affect the indoor air and roof surface temperature of the roofs during the hot summer days.

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Abbreviations

ρ :

Density (kg/m3)

C p :

Specific heat capacity (J/kg K)

T :

Temperature (K)

λ :

Thermal conductivity (W/m K)

Q :

Heat source (W)

ϕ :

Heat flux density (W/m2)

μ :

Dynamic viscosity (Pa s)

λ r :

Thermal conductivity of the aluminium sheet (W/m K)

h o :

Convective heat transfer coefficient between outdoor air and aluminium reflector (W/m2 K)

T o :

Outdoor air temperature (K)

T re :

Temperature of external surface of the reflector (K)

T gap :

Temperature of air in the gap (K)

T ri :

Temperature of internal surface of the reflector (K)

α r :

Absorption coefficient for solar radiation

ε r :

Surface emissivity

σ :

Stefan–Boltzmann constant: σ = 5.67e−8 (W/m2K4)

T sky :

Sky temperature (K)

E :

Solar radiation (W/m2)

h a :

Convective heat transfer coefficient in air gap (W/m2 K)

T c :

Temperature of composite (K)

r :

Ratio of surface emissivities

References

  1. Alavez Ramirez, R., Castillo, F., Dominguez, V., & Guzman, M. (2012). Thermal conductivity of coconut fibre filled Ferro cement sandwich panels. Construction and Building Materials,37, 425–431.

    Article  Google Scholar 

  2. Alavez Ramirez, R., Castillo, F., Dominguez, V., Guzman, M., & Romero, J. (2014). Thermal lag and decrement factor of a coconut-ferrocement roofing system. Construction and Building Materials,55(31), 246–256.

    Article  Google Scholar 

  3. Alvarado, J. L., Terrell, W., Jr., & Johnson, M. D. (2009). Passive cooling systems for cement-based roofs. Building and Environment,44, 1869–1875.

    Article  Google Scholar 

  4. Gao, Y., Xu, J., Yang, S., Tang, X., Zhou, Q., Ge, J., et al. (2014). Cool roofs in China: Policy review, building simulations, and proof-of-concept experiments. Energy Policy,74, 190–214.

    Article  Google Scholar 

  5. Mintorogo, D. S., Widigdo, W. K., & Juniwati, A. (2015). Application of coconut fibres as outer eco-insulation to control solar heat radiation on horizontal concrete slab rooftop. Procedia Engineering,125, 765–772.

    CAS  Article  Google Scholar 

  6. Pisello, A. L., Piselli, C., & Cotana, F. (2015). Thermal-physics and energy performance of an innovative green roof system: The Cool-Green Roof. Solar Energy,116, 337–356.

    Article  Google Scholar 

  7. Rodriguez, N. J., et al. (2011). Assessment of coconut fibre insulation characteristics and its use to modulate temperatures in concrete slabs with the aid of a finite element methodology. Energy and Buildings,43, 1264–1272.

    Article  Google Scholar 

  8. Sabah M, R., Ansari, M., & Saleh H, M. (2012). A study on mechanical, thermal and morphological properties of natural fibre/epoxy composite. Design for Scientific Renaissance,1(5), 267–296.

    Google Scholar 

  9. Yalley, P. P., & Kwan, A. S. K. (2009). Uses of coconut fibres as a enhancement of concrete. Cement and Concrete Composite, Indian Coconut Journal,15, 54–73.

    Google Scholar 

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Correspondence to V. Vinod Kumar.

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Kumar, V.V. Investigation of the thermal performance of coconut fibre composite with aluminium reflector cooling roofs. Environ Dev Sustain 22, 2207–2221 (2020). https://doi.org/10.1007/s10668-018-0285-x

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Keywords

  • Global warming
  • Coconut fibre composite
  • Heat flux
  • Reflectors
  • Thermal comfort