Optimization For Lenght and Diameter of Capillary Tube

Hı everyone;

I am new at site and ı am an cooling engıneer at refrigerator factory , for our refrıgerator, ı want to make an ımprovement for thermodynamıcm elements evaparator,condenser,capılllary tube,compressor, Could you please help me about the role of the capıllary tube on p-h and t-s dhygram