Here are some of the things that I included on my cheat sheets (I took HVAC and Refrigeration back in October 08)
I don't have the actual sheets on me right now but here's what i remember:
A picture of a psych chart, with arrows pointing in the direction of dehumidification, humidification, heating, cooling and all the combinations.
Q=mc(Delta T) - for air: Q=1.08(CFM)(Delta T)
Constants = 8.314 lb/gal, air 13.75 ft^3/lb, h20 = 62.4 lb/ft^3, etc.
Enthalpy wheel effectiveness equation
Condensate removal equation
A picture of a vapor compression cycle - ph diagram - showing things like condenser heat rejection, de-superheat, superheat, constant entropy line, refrigeration capacity, etc. How the PH diagram relates to condenser, compressor, evap, expansion valve.
Range, approach, efficiency of cooling tower equation.
air washer saturation
friction head, velocity head equation both for psi, ft head.
HP equation for both fans and pumps
number of poles/rpm equation, specific speed equation
Relative humidity equation
Q = 4.5*CFM*(Change in enthalpy)
Humidifier equation
Sound equations - check ASHRAE
Vp = (V_fpm/4005)^2
Speed of sound equation
Buoyancy
Carnot efficiency equation
Mollier diagram showing things like steam expanding isentropically, etc.
Heat exchanger effectiveness equations
Pump/fans similarity equations
Bypass factor equation for coils
A bunch of steam sample problems
kinematics
elastic deformation
thermal expansion
combustion cycle diagrams -otto, carnot
Principle stresses
Pressure vessels