Patent ID: 7380963

Claim:
Method of controlling a cooling process of a lamp ( 10 ), in particular a High Power lamp, wherein the cooling process takes place by means of a cooling medium flowing by the lamp ( 10 ), and wherein an actual rate of flow of the cooling medium is controlled so as to equal a required value that is associated with the operating power of the lamp ( 10 ), further comprising: measuring a value of pressure of the cooling medium, wherein the pressure includes a total of an environmental atmospheric pressure and an excess pressure of the flow of the cooling medium with respect to the environmental atmospheric pressure; measuring a value of pressure drop of the cooling medium across an orifice positioned in the flow of the cooling medium; determining a value of density of the cooling medium on the basis of the measured value of the pressure of the cooling medium; and determining a rate of flow of the cooling medium on the basis of the determined value of the density of the cooling medium and the measured value of the pressure drop of the flow of the cooling medium across the orifice.