Date of Publication

3-2024

Document Type

Master's Thesis

Degree Name

Master of Science in Mechanical Engineering

Subject Categories

Engineering | Mechanical Engineering

College

Gokongwei College of Engineering

Department/Unit

Mechanical Engineering

Thesis Advisor

Aristotle T. Ubando

Defense Panel Chair

Laurence A. Gan Lim

Defense Panel Member

Ivan Henderson V. Gue
Robby B. Manrique

Abstract/Summary

Air conditioning has been an integral part of modern living, primarily aimed at providing thermal comfort. However, it is often overlooked that these systems are heat pumps that require substantial energy to transfer heat from a cooler to a warmer heat reservoir. It is for this reason that air conditioning represents a significant portion of global energy consumption and serves as a significant source of waste heat. This study offers a way to recover waste heat from a window-type room air conditioner by integrating a rotary desiccant wheel. The wheel dehumidifies recirculated moist air before cooling, thereby reducing the latent load on the evaporator. On the outdoor side, the exiting warm air from the condenser regenerates the desiccant wheel without the need for an electric heater. Waste heat from the condenser is utilized to evaporate the adsorbed water molecules in the desiccant. The final temperature of the air exiting the desiccant wheel on the condenser side also cools down via evaporative cooling. Aside from increasing the cooling capacity of the air conditioner for sensible cooling, the proposed system also contributes to the mitigation of the urban heat island effect by minimizing the thermal energy that escapes to the environment. In this study, a quasi-analytical analysis is used to mathematically model the desiccant wheel and the overall system. Experimental data from an existing study of similar magnitude from the literature is used to validate the model. The model is then used to characterize the influence of factors such as ambient air conditions, rotational speed of the desiccant wheel, and desiccant material type to the overall performance of the system. Finally, an optimization is conducted to find the optimal values of the independent variables mentioned.

The proposed system proved to have successfully recovered waste heat from the conventional design of a window-type room air conditioner. In the design framework, it was found that the new specific enthalpy of process air before going through the evaporator was decreased by about 3 kJ∙kg-1 by the introduction of a desiccant wheel. In consequence, the cooling capacity of the system was increased by about 2,357.45 kJ∙hr-1 (18.5 %). Furthermore, the temperature of the exhaust air through the condenser was decreased by around 2 °C, mitigating the effects on the urban heat island effect.

Abstract Format

html

Language

English

Format

Electronic

Keywords

Air conditioning; Heat recovery

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Embargo Period

3-2027

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Available for download on Monday, March 01, 2027

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