Air-conditioning circuit, in particular for motor vehicle

The circuit (1) has an air-conditioning loop (3) provided with a condenser (5) that allows a heat transfer between a refrigerant and a coolant i.e. glycol water. The loop and a coolant circuit (7) comprise heat exchangers (9, 11) respectively for under cooling of the refrigerant and cooling of the coolant. The exchangers are crossed by an air flow (F) for transferring heat with the exchangers, where an S/St ratio of a heat transferring surface (S) of one of the exchangers relative to a surface for passage of the air flow through the exchangers is equal to 0.15 and greater than 0.7. The heat exchangers are designed as guide-tube type heat exchangers. The refrigerant is an R1234yf-type refrigerant or an R134a-type refrigerant.