18 May 2017

P.3.1.7 Dynamic Modeling of a Personal Cooling Device with PCM Storage


A personal cooling device, named Roving Comfort (RoCo), has been designed and a prototype has been fabricated at the Center for Environmental Energy Engineering. RoCo is capable of following occupant(s) autonomously and providing cooling/heating as needed. The device helps reducing building electricity consumptions by enabling extended thermostat settings for building air conditioning systems, i.e., 4°F above or below traditional cooling/heating set point with improved thermal comfort of occupants. It has a phase change material (PCM)-embedded condenser to store the rejected heat from the vapor compression cycle. Once the PCM storage is full, RoCo switches into a thermosiphon mode to re-solidify the PCM material. To obtain a better understanding of the RoCo operation and design better components, a dynamic system model capable of depicting the time-dependent performance of RoCo is developed using the Modelica language. A previously developed in-house HVAC component library, along with a newly developed PCM embedded HX model and thermosiphon model, is used to simulate both the vapor compression mode and thermosiphon mode. The simulated results are validated against the experimental data obtained from prototype tests and the model is used to optimize the cyclic operation of the device for continuous operation.