FST 110B

Lecture 1

· Introductions

· Course Objectives

· Description of Lecture Outline

· Heat content and rate of heat transfer

Heat … A manifestation of energy.

What is energy?

· Energy flows in various forms: electrical energy and mechanical work

· Energy is stored: chemical energy in fuel, strain energy in a spring

· Energy is interconvertible with mass

Enthalpy or Heat content:

Heat energy stored in an object.

Internal energy—a result of the activity of atoms

Heat (or Enthalpy) = mass specific heat temperature difference from reference

(Reference is usually at 0 °C)

Heat content of an object

Q = m c_p DT

Where Q = enthalpy, kJ

m = mass, kg

c_p = specific heat

DT = temperature difference,°C

Rate of change of heat content

e.g. in case of a liquid flowing in a pipe, due to heat transfer, its temperature changes from inlet to exit.

q = c_p DT

Where

q = rate of change of heat content, kJ/s

= rate of mass flow , kg/s

c_p = specific heat, kJ/kg C

DT = temperature difference from inlet to exit, °C