The Electromagnetic Capstone Group: Comprehensive Heating, Cooling, and Electrical System for Electromagnet

Overview

The Electromagnetic Capstone Team was tasked with designing a cooling system, adding a terminal block, and creating housing for a tabletop E-Core magnet for the Pennsylvania State University’s Magento-Active Composites and Structure Laboratory (PSU MACS Lab). The main challenges the team faced involved creating accurate heat transfer calculations, finding the ideal temperature sensors that would not interfere with the copper coils, and finding the most cost-effective and efficient method for cooling. After meeting the team’s sponsor, Professor vonLockette, the main focuses of the project were decided on using temperature sensors to inform an operator of the effectiveness of the coolant, which would be in two cylinders that would encase each coil, which would then connect to a wort chiller to remove at least 1.5 kW of heat. The main deliverable of this project is a working process involving the wort chiller, Arduino, temperature sensors, enclosed casing for each coil, and a functional magnet that can run for 4-6 hours.

The team received a budget of $1000, however, the PSU MACS Lab has a grant that allowed the team to go a bit over-budget. Much of the budget was reserved for the cooling team. While the cooling team initially wanted to use a tub chiller that had a cost of about $500, a wort chiller was decided since the cost is roughly $350, and the wort chiller is more thermally efficient. The rest of the budget was used for materials for the electrical components (temperature sensors, terminal blocks, etc.) and the housing components (PVC pipe, wood, wood glue, dowels, non-ferrous nails, etc.). To complete all tasks and deliver the final working prototype, a Gantt chart was created and consistently updated. The Gantt chart allowed tasks to be separated into teams (Housing, Cooling, and Electrical), which ensured that each member was contributing, no one was overwhelmed, and that swift progress was occurring.

Objectives

The sponsor envisions that this project will have three deliverables.

1) A Cooling system: A standard cooling method for these magnets is to flow suitable coolant directly over the coils to extract heat, then extract heat from the coolant before recirculating it back through the coils. This will require selection of a suitable coolant material (one method uses deionized water). The system should display the current magnet and coolant temperatures at a minimum. It would beneficial if status lights (red-yellow-green) based on preset temperatures were also displayed. Quick disconnects and valving should be included such that coolant lines can be easily disconnects and reconnected from the magnet for transport. Specifications for a suitable laboratory chiller to remove heat from the coolant should be determined and then the device should be procured and integrated with the magnet.

2) The electrical system: The magnet is powered by the 30A supply to which it is hardwired. Instead, the sponsor seeks to have the magnet wired to an enclosed terminal block that can also be dis/connected separately to a power supply. There should be a manual shutoff in this terminal.

3) The housing: Herein the sponsor seeks housing that a) reversibly fixes the magnet level on a transportable, non-conducting platform, b) has space for mounting the terminal block from (2), c) allows orderly arrangements of all electrical wiring and coolant lines, and d) provides a riser in between the magnet poles that is level with the pole faces. A bonus would be if the riser is 1/4-20 tapped on 1” spacings.

Approach

Prior to this report, the team worked through planning, concept development, system-level design, and detail design. The team broke into three groups: housing, cooling, and electrical. Each group generated concepts via sketches, and the best ideas were combined until the final concepts were chosen. From there, each group worked differently to create the concepts. The housing group designed the concept first on SolidWorks, which can be seen in Figure 1. The purpose of this was to see if the design was practical before spending any of the budget on materials. The SolidWorks design went through a few different iterations, but once the design was determined to be practical and efficient, the housing group purchased the needed materials such as PVC pipe, caps, wood, wood glue, etc. With these materials, the housing group was able to manufacture the original concept.
The cooling group began with heat transfer calculations to determine the type of chiller to buy. Originally, the cooling group wanted to purchase a tub chiller, which is about $500. Eventually, the group decided that a wort chiller would not only be cheaper ($350), but also more effective because a wort chiller is a crossflow heat exchanger.
Finally, the electrical group researched various temperature sensors that could be used in the system. The main obstacle was that these sensors could not have a high magnetic force, since they would impact the efficiency of the magnet. The rest of this report details the processes and results of combining these three groups into one system.

Outcomes

For housing, a lot of iterations and ideas were attempted through design drawing and CAD sketch-ups. Using Solidworks, the team was able to determine whether the flow simulations were affected based on the materials used. What was ultimately decided on was the use of a wooden base in conjunction with the PVC pipes being used as the chambers for holding the water used to cool the coils. Using wood as the material for the base allowed the team to take advantage of its rigidity and affordability. Wood was also prioritized as a material of choice since it would not interfere with the metal components of the magnet and disrupt the magnetic field. PVC pipes were cut close to size to allow for a tight fit between the ridges of the PVC and the magnet. The team’s intention was to use rubber gasket material to strengthen the seal between the PVC and the magnet to prevent leakages and issues with pressure uniformity. Unfortunately, there were fitting issues with the joints used to adhere the cooling pipes to each other which resulted in minor leakages in the system. In the future, the team hopes to dedicate more time to re-fitting these joints to eliminate the chances of this occurring. However, due to limitations with the budget, the team had to utilize the joints that were bought. When it comes to electrical its overarching goal is to provide a live feed of accurate temperature readings of the coil and the wort chiller itself. In the beginning, testing the sensors themselves was necessary. To start, testing a single amplifier and thermocouple was performed to ensure a proper interface with the Arduino. Following that, the need for multiple sensors and amplifiers at the same time is needed on one microcontroller. After testing multiple different code iterations, a code that can read all the sensors was crafted shown in Appendix A. After the sensor tests were complete, the need to display the temperature readings is needed. To start, similarly to the thermocouple, it is started with one display, learning along the way how to apply the display. Once one display is successfully working, the same idea is then applied to each of the displays. Once all the components were working, some of the sensors seemed to be reading false temperatures. After some testing, and some logic we found that the sensors all read within 1-degree Celsius of the actual temperature, which in this case should suffice. Unfortunately, after testing the display box and thermocouple numerous times one of the pinout wires broke in the microcontroller. With this issue at hand, the team decided that different digital inputs could be used. Unexpectedly, after rewiring and checking over the wires’ placement and the code called, the amplifier showed an error temperature that is common for these RTD amplifiers showing a temperature of –242. With the numerous tests and scrolling through suggestions online we deduced that the amplifier may be not functional anymore. Fortunately, the amplifier that broke is for the inlet of the cold temperature reading, which comparably to the other sensor outputs, is one of the least important if not the least important. At the end of prototyping and testing, the electrical system overall works, with a functioning code and 5 successfully displayed temperatures.
The cooling system met every requirement specified by the sponsor. It remained watertight and demonstrated adequate fluid flow. While we were not able to test the full cooling abilities of the system due to leakage in the magnet housing, the heat transfer equations proved that the system would theoretically be able to cool the magnet to workable temperature and extend the running time. Every piece of equipment and fittings worked as intended and the system projects a running time of roughly 6 hours which is dependent on the pump running time assuming overheating of the pump after a given time, based on the pump specifications. Permitting the pipes surrounding the magnet are sealed in the future, the cooling system should be capable of removing the required 1.5 kW of heat based on the heat transfer calculations.