Why, what would happen to my lettuce if I set the thermostat near the cooling element to e.g. 3°C and have the cabbage be somewhere between that and 4.3°C?
Unless I'm very mistaken, this 1.5 degree delta is between the hot side (the condenser at almost your room temp) and the cold side (evaporator inside the fridge).
That is, if you want to chill your cabbage to 4.3 degrees C, your room temp should be not more than 5.6 degree C. Or... if it's 25 degrees outside, in an ideal case your cabbage is 23.7 degrees cool.
Btw, max theoretical COP increases rapidly as T'hot - T'cold shrinks to zero. Your practical AC or fridge delta T is much more than that, depending on the weather.
That is, if you want to chill your cabbage to 4.3 degrees C, your room temp should be not more than 5.6 degree C. Or... if it's 25 degrees outside, in an ideal case your cabbage is 23.7 degrees cool.
Btw, max theoretical COP increases rapidly as T'hot - T'cold shrinks to zero. Your practical AC or fridge delta T is much more than that, depending on the weather.