Newton's formula for convective heat transfer from a fluid to a metallic wall or from a metallic wall to a fluid is

(where, Q = heat transfer by convection in J/S, h = heat transfer or film coefficient in J/m2 Cs or W/m2 C, a = surface area through which heat is transferred in m2, ts = temperature of the surface or wall in °C and tf = temperature of the fluid in °C)

Explanation:

Newton's Formula for Convective Heat Transfer:

• Newton's formula for convective heat transfer describes the rate of heat transfer from a fluid to a metallic wall or from a metallic wall to a fluid via convection. The formula is expressed as:

Q = ha(t_s - t_f)

Where:

• Q: Heat transfer by convection in Joules per second (J/s) or Watts (W).
• h: Heat transfer or film coefficient in J/m²°C·s or W/m²°C.
• a: Surface area through which heat is transferred in square meters (m²).
• t_s: Temperature of the surface or wall in degrees Celsius (°C).
• t_f: Temperature of the fluid in degrees Celsius (°C).

Working Principle:

Heat transfer by convection occurs when a fluid (liquid or gas) comes into contact with a solid surface (e.g., a metallic wall). The temperature difference between the fluid (tf) and the solid surface (ts) drives the heat transfer process. Newton's law of cooling provides a mathematical relationship for this process, indicating that the rate of heat transfer is proportional to:

• The temperature difference (ts - tf).
• The surface area (a) exposed to heat transfer.
• The convective heat transfer coefficient (h), which depends on the properties of the fluid and the nature of the surface.

The formula Q = ha(ts - tf) accurately describes this phenomenon and is widely used in engineering calculations for convective heat transfer analysis.