ME heat and flow

what causes conduction

vibrations + collisions in atoms/molecules

conduction occurs in

solids, liquids and gasses

we calculate surface area only in

2 dimensions

Importance of studying heat + flow

cooling electronics + fish friendly pumps

as microelectronics get smaller

more heat is generated per square centimetre

Water levels are controlled by

pumps

pumps

must not be a hazard for fish + allow fish migration

What causes heat transfer via convection

the movement of fluid transports heat

convection ocours in

liquids and gasses

Natural convection

density differences from temp changes (convection current, heat rises)

Forced convection

caused by external motion (Fan blowing across hot surface)

heat always flows

from hot to cold

dQ/dt (what it stands for + units)

heat flow per second in watts

Equation for conduction

dQ/dt=kA(T2-T1)/l

what is k and its units

it is a proportionality constant indicating thermal conductivity measured in W/mK

Equation for convection

dQ/dt=hA(T2-T1)

what does h stand for + units

convective heat transfer coefficient W/m²k

when using air we have to consider

both conduction and convection

in solids we only have do consider

conduction

tan(A plus B)

tan(A) plus tan(B) divided by 1 minus tan A times tan B

tan(A minus B)

tan(A) minus tan(B) divided by 1 plus tan A times tan B

tan(A+B)

tan(A)+tan(B)/1-tan(A)tan(B)

tan(A-B)

tan(A)-tan(B)/1+tan(A)tan(B)

electrical resistance

thickness or length divided by k times area

R=

L/(K x A)