comparison to single stage refrigerant cooling there are a number of variables involved in cooling or removing heat energy from a first fluid stream in heat transfer contact with a second fluid stream including the temperature difference between the two fluids the area of contact between the two streams and the relative volumes of the two streams in the present situation and in chiller assembly 11 two stages of heat transfer occur simultaneously throughout the chiller assembly in the first stage the first fluid is the natural gas flowing through jackets 17 and the second fluid is the refrigerant flowing through tube 18 to achieve sufficient cooling of the natural gas to condense hydrocarbons such as propane and butane from the stream in a heat exchanger of reasonable size for use in a wellhead application requires a certain volume of refrigerant a certain area of contact and a certain temperature difference which parameters can be readily determined the problem inherent in the use of single stage refrigerant systems is efficiently and economically reducing the temperature of the refrigerant sufficiently to provide the required cooling capacity the use of conventional compressor condenser technology to achieve the required temperature drop in the required volume of refrigerant is economically impractical the present invention overcomes the problem inherent in the use of a single stage refrigeration.