Athin isothermal disk, having a diameter of 1.8 cm, is maintained at 40◦C and buried in a semi-infinite medium at a depth of 2 cm. The medium has a thermal conductivity of 0.8 W/m· ◦C and its surface is maintained at 15◦C. Calculate the heat lost by the disk.

Problem 3 A novel material is suddenly exposed on one side to a fluid material. The material has an overall thermal gradient of °C W -7,000 with a thermal conductivity of 23.8. The fluid m m.K • has a temperature of 30° C and a heat transfer coefficient of 325 W m². K. material. . Calculate the temperature at the surface of the

2-2 A certain material 2.5 cm thick, with a cross-sectional area of 0.1 m², has one side maintained at 35°C and the other at 95°C. The temperature at the center plane of the material is 62°C, and the heat flow through the material is 1 kW. Obtain an expression for the thermal conductivity of the material as a function of temperature.

A copper electric wire of radius R, = 1 mm is isolated by a layer of PVC so that the outer radius of the wire Rg = 2 mm, as shown in Figure below. The wire exchanges heat with the air at 20°C according to a heat transfer coefficient h=20 W/m2°c: Given that : k=copper electrical conductivity=4.0 × 1070hm-'m¯! kpvc= PVC thermal conductivity = 0.3- m°C kco = copper thermal conductivity = 100 m°C %3D (amp/m)² And that the electrical heating source is given by : S, amp²s /kgm³ If the temperature (T,) on the outer surface (r = RG) is 25°C, what is the electrical current C (amp) that passes through this wire? Dont forget to state your hypothesis clearly.     Hi, Could you please tell me what the book's name is? Thank you!

A large slab of aluminum has a thickness of 10 cm and is initially uniform in temperatureat 400◦C. It is then suddenly exposed to a convection environment at 90◦Cwith h=1400 W/m2 · ◦C. How long does it take the center to cool to 180◦C?

Please answer A