1. -:FABRICATION AND DETERMINATION OF CRITICAL THICKNESS OF SPHERICAL OBJECTS:- BY:- UNDER THE GUIDANCE OF: ANURAG TIWARI ASHWINI KUMAR VERMA MR . SUMIT TIWARI EMAM RAZA PANKAJ BARANWAL

2. CONTENTS: INTRODUCTION. OBJECTIVE OF PROJECT. LINE DIAGRAM. CONSTRUCTIONAL DETAIL. REFERENCES. 3. -:INTRODUCTION:- It ismaximum thicknessof insulator over thesphereat which weobtain maximum heat transfer rate. When radiusof theinsulator isincreased beyond acertain limit theheat transfer rateinstead of increasing start to decrease. Thecritical radiusof insulation for aspherical shell:- Thecritical radiusof insulation dependent on thermal conductivity of theinsulation (k) and the external convection heat transfer coefficient(h). Adding moreinsulation to awall or to theattic alwaysdecreasesheat transfer sincetheheat transfer areaisconstant, and adding insulation alwaysincreasesthethermal resistanceof the wall without increasing theconvection resistance. Theheat transfer from thespheremay increaseor decrease, depending on which(conduction or convection) effect dominates. 4. -: OBJECTIVEOFPROJECT:-:- We come across different situation where the rate of heat transfer after applying insulation is required to be either increase or decreased. Obtain the desired heat transfer rate over the spherical object after insulating the object. We can estimate optimum value of thickness of insulation required for desired heat transfer rate. Surplus insulating material can be avoided hence material saving. 5. -:LINE DIAGRAM OF CRITICAL THICKNESS OF INSULATOR ON SPHERE:- The variation of heat transfer rate with the outer radius of the insulation r2 when r1 < rcr. An insulated sphere exposed to convection from the outer surface and the thermal resistance network associated with it. 6. -:CONSTRUCTION DETAIL:- Consist of following main components:- 1. Spherical object. 2. Insulating material. 3. External source like fan, air-conditioning, wind blower etc. Assumptions:- 1. Heat transfer from the ball is steady since there is no indication of any change with time. 2. Heat transfer is one-dimensional since there is thermal symmetry about the midpoint. 3. Thermal properties are constant. 4. The thermal contact resistance at the interface is negligible.. Insulation Properties :- The thermal conductivity of insulator cover is given to be k = .. W/mC. 7. -:REFERENCES:- www.tririg.com www.wikipedia.org Nptel.iitm.ac.in 8. THANK YOU