Thermal Storage
Using our functional requirements and technical intuition, we were able to develop several ideas of what our heat exchanger could physically look like. After this initial concept generation, we discussed the important factors and questions that would influence our concept selection as we moved forward with our prototyping process. The overall goal of the thermal storage sub-group is to store thermal energy in a phase change material and transfer that energy to air for HVAC purposes as efficiently as possible. With this goal in mind, we highlighted four different factors to think about: heat transfer, pressure drop, assembly, and cost. After these initial considerations, we then looked to evaluate each influence in the context as senior design students with limited time and resources.
Thermal Comfort
First, we needed to determine the proper size and necessary material of the ducts based on our constraints. We needed to consider how to minimize pressure drop, which is the difference in pressure at the inlet and outlet. A lower pressure drop means less energy wasted by the system resulting in a higher energy efficiency. The major losses in pressure are impacted by the changes in velocity, so we aimed to minimize the change in airflow velocity between the inlet and outlet. We conducted a series of calculations to determine the ideal sizes of the duct outlets. We also needed to determine how our design could minimize minor losses within the ducts, which are changes in pressure due to the design of the ducts and airflow path. As the air inside the ducts moves from the heat exchanger section to the ducts, the changes in shape will lead to this pressure loss. Additionally, we searched for available parts and materials from common suppliers to compare prices and select our prototype design. Following this, we modeled the changes in velocity and pressure of our final design using CFD (Computational Fluid Dynamic) software. We also talked with the machine shop technicians regarding their capabilities to construct custom parts that we might need.