Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Mechanical Engineering

Committee Chair/Advisor

Omar, Mohammed A

Committee Member

Grujicic , Mica

Committee Member

Haung , Young

Committee Member

Daqaq , Mohammed


This dissertation discusses the effect of manipulating the relative humidity RH levels inside vehicular cabins on the thermal comfort and human occupants' thermal sensation. Three different techniques are used to investigate this effect. Firstly, thermodynamic and psychometric analyses are used to incorporate the effect of changing RH along with the dry bulb temperature on the human comfort window. Specifically, the study computes the effect of changing the relative humidity on the amount of heat rejected from the passenger compartment and the effect on occupants comfort zone. A practical system implementation is also discussed in terms of an evaporative cooler design. Secondly, a 3-D finite difference simulation is used to predict the RH effects on the thermal sensation metrics. The study uses the Berkeley and the Fanger models to investigate the human comfort using four specific perspectives; (i) the effect on other environmental conditions, (ii) the effect on the body segments temperature variation within the cabin, (iii) the cabin local sensation (LS) and comfort (LC) for the different body segments; in addition to the overall sensation (OS) and overall comfort (OC), (iv) the human sensation is also measured by the Predicted Mean Value (PMV) and the Predicted Percentage Dissatisfied (PPD) indices during the summer and the winter periods following the Fanger model calculations. Thirdly, the analysis and modeling of the vehicular thermal comfort parameters is conducted using a set of designed experiments aided by thermography measurements. The experiments employed a full size climatic chamber to host the test vehicle, to accurately assess the transient and steady state temperature distributions of the test vehicle cabins. The experimental and simulation work show that controlling the RH levels along with the Dry Bulb Temperature helps the A/C system achieve the human comfort zone faster than the case if the RH value is not controlled. Also, the results show that changing the RH along with Dry Bulb Temperature inside vehicular cabins can improve the air conditioning efficiency by reducing the amount of heat removed. Finally, this work has developed the passenger thermal-comfort psychometric zones during summer and winter periods using Berkeley and Fanger models.



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