Indicate which component responsible for the production of cold in the cycle of a refrigerating unit or a chiller? evaporator or expansion valve?

cooling is achieved by expansion valve due to its throttling affect. If there is no expansion valve the evaporator will not work

1. chilled water system - The chilled water out of the evaporator circulates through the FCU (load and heat exchanger) and cold air blown out via fan. The temperature of the water as the median exchanger increases. The  water with higher temperature is pumps back to the evaporator via chillers' pump(s) .

2. Refrigerant system- The refrigerant system has low pressure and high pressure zone. The low pressure zone after expansion device, the refrigerant gas passes through evaporator and absorbs the heat of the chilled water (through shell and tube heat exchanger). Then heated refrigerant compressed through the compressor and now in high pressure zone(after compressor), enters condenser (the second heat exchanger). 

3. Condenser system- The high pressure hot gas changes its heat through the condenser heat exchanget to the other median (water or air) depending to the chiller, air or water cooled system. The hot compressed gas after passing the condenser changes the phase to the liquid. Liquid refrigerant passes through the expansion device and changes the phase to gas which can absorb heat. The cycles repeats again and again.

Condenser responsible for condensing refrigerant ------ latent heat removal

Expansion valve responsible for decrease refrigerant temperature -------- sensible heat removal

Evaporator responsible for evaporate refrigerant ----------- latent heat gain

Evaporator Is resposible for cooling