Cooling Coil Design

[Rayin]

Hi Friends..
I have to make an evaporator for a refrigerator having internal useful space 500mm Wide x 500 mm Deep x 1420 mm High.
Please see the attached sketch.(Condensing unit is mounted below this space).

The Refrigerator body and door are made out of 0.8 mm thick stainless steel (both inner and outer) and 50 mm thick PUF injected insulation. It has one no. hinged door with a clear opening space of 460x1300 mm.

The cooler is used to keep fresh meet (Lamb) approximately 15 to 20 Kg. There is 1 no. 32 W light inside. Room temperature 20 to 22 deg.C. Initial cooling time 3 hours.
Compressor to be used SC15G of danfoss made in Germany. Refrigerant 134a.

My questions are
1. What should be the total length of copper coil to make evaporator?

2. What is the equation to find out the total length?

3. What should be the space between fins?

4. Is it true that, if we use forced air evaporator for meat, color of meat changes?.

5. How do we estimate the number times of door opening?

Thank you very much indeed for all in advance.
Regards
RAYIN