Thermophysical properties of selected cash crops grown in Ghana
In this thesis, the influence of moisture on selected physical, compressive and thermal properties of cocoa beans, shea and cashew nut and kernel were studied. Standard methodologies that have been accepted internationally and used by several researchers globally were used for the determination of the selected properties in moisture content ranges normally used for the postharvest processing of the selected crops. The results of moisture variationon physical properties of cocoa beans and cashew kernels such as 1000-bean mass,true density, porosity, emptying angle of reposeandstatic coefficient of friction showed increasing trends with linear relationships while bulk density decreased linearly for cocoa bean and cashew kernel samples. The compressive strain and Young’s Modulus for cocoa beans decreasedlinearly with moisture from 0.009 to 0.0045, and 1300 to 205 MPa respectively. However the compressive stress decreased exponentially with increasing moisture content from 1.5 -0.3 MPa while the crushing energy had more positive linear function with moisture content and increased from 0.013 -0.2 J. For shea kernel, compressive stress, compressive strain and Young’s Modulus decreased linearly from 2.0 -0.8MPa, 0.0085 -0.002mm/mm and 2000 –100MPa with increasingmoisture content. Crushing energy increased non-linearly from 0.005 -0.13mJ in the moisture content range of 5% -24% w.b. The compressive stress, strain, and Young’s modulus for the cashew kernel increased from 0.214 -1.214 MPa, 0.355 -0.472 mm/mm, and 2.446 -6.416 MPa respectively as moisture content increased from 5.0 -9.0% wb. Thermal conductivity increased linearly for groundcocoa beans sample from 0.0243-0.0311 W/oCm and for ground shea kernels from 0.0165 -0.0458 W/oCm in the moisturecontent range of 12.59 -43.84%w.b. at a constant bulk density of 295 kg/m3.Specific heat, thermal conductivity and thermal diffusivity for ground cashew kernel were found to increase linearly from 1586 –1756J/kgº., 0.2103 -0.2296W/mK and 2.369×10-7-2.588×10-7m2/s with increasing moisture content from 5.0 -9.0% w.b.
A Thesis submitted to the Department of Agricultural Engineering, Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food and Postharvest Engineering, 2014
Cocoa beans, Shea Kernel, Cashew Kernel, Physical properties, Compressive properties, Thermal properties, Moisure content