The substance methane has the following properties: normal melting point: 90.7 K normal boiling point: 109.1 K triple point: 9.2×10-2 atm, 90.6 K critical point: 45.7 atm, 190.7 K At temperatures above 190.7 K and pressures above 45.7 atm, CH4 is a . CH4 does not exist as a liquid at pressures below atm. CH4 is a at 9.20×10-2 atm and 117.0 K. CH4 is a at 1.00 atm and 106.0 K. CH4 is a at 8.62 atm and 82.7 K.

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.