# Calculate the time ⏱️ it will take for cooling down a cup of hot milk 😙 💨 ☕️

How can I calculate the time ⏱️ it will take for me to cool down a cup of hot milk ☕️ by blowing over it 😙💨?

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How can I calculate the time ⏱️ it will take for me to cool down a cup of hot milk ☕️ by blowing over it 😙💨?

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## Comments

Hi

The process of cooling by blowing over something is called Forced convection. The rate of heat transfer can be computed using the Newton's law of cooling - which states that the convection heat transfer rate, q", is directly proportional to the difference between the surface and fluid temperatures. In mathematical terms,

q" = h(T_s - T_inf)

where:

q" - convection heat flux (W/m^2),

h - proportionality constant referred to as the heat transfer coefficient (W/(m^2.K)),

T_s - surface temperature, and

T_inf - bulk fluid temperature.