This research used R-134a or Tetrafluoroethane refrigerant (CF3CH2F). This refrigerant is included in HFC (Hydro Fluoro Carbon) which has no Cl (Chlor) element and is a colorless, odorless, boiling agent at room temperature and can be used in low pressure, R-134a refrigerant used in refrigeration system modified modified vapor compression, the purpose of this study was to determine the effect of cooling load on the evaporative heat transfer coefficient in the vertical pipeline. The method used in this study is an experimental method by varying the cooling load capacity of the evaporator and also adjusting the frequency of the inverter to adjust the variation of refrigerant flow rate. The evaporator is placed in a tub of 25 cm x 15 cm x 20 cm which will be filled with water and the discharge is measured using a water rotameter. The test is carried out by using a simple vapor compression test instrument modified by adding heater, test section, and orifice. At the specified point put pressure gauge and thermocouple for the pressure and temperature data retrieval. The refrigerant used is R-134a. The results of this study indicate that the value of the evaporative heat transfer coefficient increases with the increase of cooling load capacity given into the evaporator, with the added cooling load per one variation of the mass flow rate, the highest (hevap) coefficient value is 4836, 089 W / m2K at a frequency variation of 16 Hz inverters. The highest cooling load capacity (1030,20 Watt) is the variation of 24 Hz inverter frequency. The value of the lowest heap evaporation (hevap) coefficient is 707,25 W / m2K ie at 24 Hz frequency, the lowest cooling load capacity is 281,75 Watt at the frequency of 18 Hz.