In light of concerns about environmental protection of the earth and scarcity of fossil fuels, the economization of fuel consumption by vehicles and the reduction in greenhouse gas emissions has become a major global priority. ISG (Idle Stop and Go) system is a vehicle tec-hnology that decreases fuel consumption and exhaust gas by ceasing the operation of an engine during idle mode. In addition, the ISG system increases mileage in the case of waiting frequently at traffic lights during traffic congestion, further protecting the environment from unnecessary pollution. An ISG system, like the one mentioned above, is usually installed in a hybrid electric vehicle due to its known high energy efficiency but nowadays, the system implementation has been widened to include internal combustion engine vehicles. However, vehicles with an ISG system cannot effectively run an air-conditioning system, as the compressor stops that receives driving force via the V-belt, as the engine stops. That is why vehicle air-conditioning systems now face challenges in maintaining thermal comfort of the cabin passengers. To resolve these issues, many possible technologies are being considered, and research has been conducted on thermal storage systems filled with PCMs (Phase Change Materials) in the heat exchanger as a possible solution that provides thermal comfort within a short period of time in the cabin, such as during stops at traffic lights and ad hoc parking (Ao et al., 2007). Konaka and Matsuo (2000) developed a thermal storage system for trucks. For the PCM, around 8 kg of water was used, while simultaneously running the existing airconditioner to operate the thermal storage system while driving; the cold conditioner operated at 26 °C for 4 hours. As a result of this study, cold storage amounted to approximately 640 Wh, which is necessary after calculation of the time needed for thermal storage during the average driving distance. After reviewing several thermal storage materials under these conditions, water has been identified as the most superior cold storage material. Various trials involving the use of an existing evaporator *Corresponding author. e-mail: dlee6@hvccglobal.com as part of a vehicle thermal storage system, have been conducted over the past few years. In particular, many efforts to integrate the evaporator and cold storage heat exchanger have been conducted in several countries in order to adapt to the limited space within vehicles (Regine et al., 2004); integral type heat exchangers for effective heat conduction between the evaporator and cold storage heat exchanger were suggested as alternatives (Cathy et al., 2002; Kitamura et al., 2004).