A novel personal cooling system (PCS) incorporated with phase change materials (PCMs) and ventilation fans: An investigation on its cooling efficiency Yehu Lu a,b , Fanru Wei b , Dandan Lai b , wen Shi b , Faming Wang a,b,n , Chuansi Gao c Guowen Song d a Laboratory for Clothing Physiology and Ergonomics (LCPE), The National Engineering Laboratory for Modern Silk, Soochow University, Suzhou 215123, China b Department of Fashion Design and Engineering, College of Textile and Clothing Engineering, Soochow University, Suzhou 215021, China c Thermal Environment Laboratory, Department of Design Science, Lund University, 22100 Lund, Sweden d Department of AESHM, Iowa State University, Ames IA 50011, USA article info Article history: Received 12 January 2015 Received in revised form 2 July 2015 Accepted 6 July 2015 Keywords: Personal cooling system Cooling efficiency Phase change material Ventilation fans abstract Personal cooling systems (PCS) have been developed to mitigate the impact of severe heat stress for humans working in hot environments. It is still a great challenge to develop PCSs that are portable, inexpensive, and effective. We studied the performance of a new hybrid PCS incorporating both venti- lation fans and phase change materials (PCMs). The cooling efficiency of the newly developed PCS was investigated on a sweating manikin in two hot conditions: hot humid (HH, 34 °C, 75% RH) and hot dry (HD, 34 °C, 28% RH). Four test scenarios were selected: fans off with no PCMs (i.e., Fan-off, the CONTROL), fans on with no PCMs (i.e., Fan-on), fans off with fully solidified PCMs (i.e., PCMþFan-off), and fans on with fully solidified PCMs (i.e., PCMþFan-on). It was found that the addition of PCMs provided a 54∼78 min cooling in HH condition. In contrast, the PCMs only offered a 19–39 min cooling in HD condition. In both conditions, the ventilation fans greatly enhanced the evaporative heat loss compared with Fan-off. The hybrid PCS (i.e., PCMþFan-on) provided a continuous cooling effect during the three- hour test and the average cooling rate for the whole body was around 111 and 315W in HH and HD conditions, respectively. Overall, the new hybrid PCS may be an effective means of ameliorating symp- toms of heat stress in both hot-humid and hot-dry environments. & 2015 Published by Elsevier Ltd. 1. Introduction Uncompensable heat stress has been considered as a common risk to impair work performance, which may lead to heat stress incidents, illnesses or even fatality (Barr et al., 2009; Chou et al., 2008; Elson and Eckels, 2015). In hot conditions, sweating is the main effective way for the human body to dissipate body heat to the environment. The excessive heat stored in the body will raise the core temperature, resulting in hyperthermia and/or heat dis- orders and thereby threatens the worker’s health and safety. Over the past few decades, various types of personal cooling systems (PCSs) have been developed to mitigate heat strain in hot en- vironments, e.g., cooling vests equipped with ice packs or phase change material (PCM) packs or frozen gel strips (Chou et al., 2008; Gao et al., 2010, 2011; Nishihara et al., 2002; Smolander et al., 2004), liquid cooling garments (Barwood et al., 2009a; Kim et al., 2011) and forced air ventilation clothing (Barwood et al., 2009b; Chinevere et al., 2008; Hadid et al., 2008; Xu and Gonzalez, 2011; Zhao et al., 2013b). In contrast to the aforementioned cooling methods, liquid cooling shows the best effectiveness in removing excessive body heat while working in hot environments (Teu- nissen et al., 2014). Nevertheless, liquid cooling garments (LCGs) are bulky, heavy and also, external pumps are needed for the movement of liquids. Therefore, LCGs restrict the user mobility and their overall cooling benefits are greatly compromised (McLellan et al., 2013). Phase change materials (PCMs) can absorb or release heat during phase change. PCMs can be easily incorporated into clothing. Although fully melted PCMs require refrigerators or cool places for solidification, PCMs with a not too low melting tem- perature (e.g., above 15.0 °C) can be solidified by conveniently immersing them into cooler water wells or underground water (Kuklane et al., 2015). PCM vests have been widely used by workers wearing protective clothing (Bennett et al., 1995; Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jtherbio Journal of Thermal Biology http://dx.doi.org/10.1016/j.jtherbio.2015.07.002 0306-4565/& 2015 Published by Elsevier Ltd. n Corresponding author. E-mail address: dr.famingwang@gmail.com (F. Wang). Please cite this article as: Lu, Y., et al., A novel personal cooling system (PCS) incorporated with phase change materials (PCMs) and ventilation fans: An investigation on its cooling efficiency. J. Thermal Biol. (2015), http://dx.doi.org/10.1016/j.jtherbio.2015.07.002i Journal of Thermal Biology ∎ (∎∎∎∎) ∎∎∎–∎∎∎