Date of Award

2018

Degree Type

Thesis

Degree Name

Master of Science in Mechanical Engineering and Applied Mechanics

Department

Mechanical, Industrial and Systems Engineering

First Advisor

Musa Jouaneh

Abstract

This thesis goes over the details of humidification and temperature modeling for an enclosed, non-hermetically sealed space. Review of common methods of thermal and humidication design was performed to detail which method is suitable for any given application. For the application of designing an enclosure for the preparation of Cryo-TEM sample grids, it was determined that system design via lumped capacitance methods was the best option. A detailed and practical analysis of the application of the lumped capacitance method is described.

A detailed overview of how to apply control of relative humidity and temperature in an enclosed space is also included. It was required to build the entire system from the ground up to implement a control scheme for the preparation of Cryo-TEM grids. This includes the design of heaters, a humidifier, an enclosure, electronics, and programming. Heating of the enclosure was accomplished through the utilization of cartridge heaters in an application to take advantage of the benefits of forced convection. Humidification was accomplished with a closed loop design where moist air is fed to the enclosure and the dry air of the enclosure is returned to the humidifier. Water vapour was produced through an ultrasonic piezoelectric transducer. Control of these elements was established via PC and electronic control.

Work has shown the effectiveness of the lumped methods for developing accurate higher order models for thermal systems. Experiments had to be performed to determine the thermodynamic parameters associated with convection required to develop the state space equations to represent the system. This is due to the many unknowns present without the use of CFD simulations. For portions of the system relying on thermal conduction, the predictive model calculated shows excellent agreement with real world data. Once the thermal model for the overall system was developed, experimentation of various inputs and changes in thermodynamics were used to verify the effectiveness of the model.

There was also a need to develop a model for humidification based on direct measurements of relative humidity. The model is based on pressure driven mass flow in terms of partial pressures and conservation of mass. This leads to a system where the active input is water vapour and the passive input being the ambient water vapour partial pressure. Since relative humidity is based off of dry bulb temperature, there was a need to develop a model to take temperature into consideration. A model was developed to consider all of these factors in a first-order system.

Available for download on Monday, July 27, 2020

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