Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 82-87). / Evaporation, a commonly found phenomenon in nature, is widely used in thermal management, water purification, and steam generation as it takes advantage of the enthalpy of vaporization. Despite being extensively studied for decades, the fundamental understanding of evaporation, which is necessary for making full use of evaporation, remains limited up to date. It is in general difficult to experimentally characterize the interfacial heat and mass transfer during evaporation. In this thesis, we designed and microfabricated an ultrathin nanoporous membrane as an experimental platform to overcome some critical challenges including: (1) realizing accurate and yet non-invasive interface temperature measurement; (2) decoupling the interfacial transport resistance from the thermofluidic resistance in the liquid phase and the diffusion resistance in the vapor phase; and (3) mitigating the blockage risk of the liquid-vapor interface due to nonevaporative contaminants. Our nano device consisted of an ultrathin free-standing membrane (~200 nm thick) containing an array of nanopores (pore diameter ~100 nm). A gold layer deposited on the membrane served as an electric heater to induce evaporation as well as a resistive temperature detector to closely monitor the interface temperature. This configuration minimizes the thermofluidic resistance in the liquid and mitigates the contamination risk. We characterized evaporation from this nano device in air as well as pure vapor. We demonstrated interfacial heat fluxes of ~~500 W/cm² for evaporation in air, where we elucidated that the Maxwell- Stefan equation governed the overall transport instead of Fick's law, especially in the high flux regime. In vapor, we achieved kinetically limited evaporation with an interfacial heat transfer coefficient up to 54 kW/cm² K. We utilized the kinetic theory with the Boltzmann transport equation to model the evaporative transport. With both experiments and modeling, we demonstrated that the kinetic limit of evaporation is determined by the pressure ratio between the vapor in the far field and that generated by the interface. The improved fundamental understanding of evaporation that we gained indicates the significant promise of utilizing an ultrathin nanoporous design to achieve high heat fluxes for evaporation in thermal management, desalination, steam generation, and beyond. / by Zhengmao Lu. / Ph. D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1988. / Includes bibliographical references. / by Ahmad Naveed Ismail. / M.S.

Thesis. (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1987. / Bibliography: leaves 122-125. / by Ming Jaw Liou. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (p. 99-100). / Buildings are one of the world's largest consumers of energy, yet measures to reduce energy consumption are often ignored during the building design process. In developing countries, enormous numbers of new residential buildings are being constructed each year, and many of these buildings perform very poorly in terms of energy efficiency. One of the major barriers to better building designs is the lack of tools to aid architects during the preliminary design stages. In order to address the need for feedback about building energy use early in the design process, a model was developed and implemented as a software design tool using the C++ programming language. The new program requires a limited amount of input from the user and runs simulations to predict heating and cooling loads for residential buildings. The user interface was created with the architect in mind, and it results in direct graphical comparisons of the energy requirements for different building designs. The simulations run hour by hour for the entire year using measured weather data. They typically complete in less than two seconds, allowing for very fast comparisons of different scenarios. A set of simulations was run to perform a comparison between the new program and an existing tool called Energy-10. Overall, the loads predicted by the two programs were in good agreement. / by Jonathan Y. Smith. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1992. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (leaves 104-106). / by Thomas H. Moyer. / M.S.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995. / Includes bibliographical references (leaf 43). / by Chun Ling Chen. / B.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, June 2005. / "May 2005." / Includes bibliographical references (leaf 27). / Haiti is the poorest country in the Western hemisphere and is in need of cheap cooking fuel source. Currently, lump charcoal, the cooking fuel of Haiti, is made by carbonizing trees in ditches before selling the charcoal at market. However, Haiti is now 98% deforested and must find a way to prepare their food that does not destroy their land. The idea for this new fuel comes from compressed and extruded carbonized bagasse, which was produced using an extruder developed in a senior product development class at MIT. Using this bagasse fuel, experiments were conducted to compare the combustion characteristics of the bagasse charcoals with wood charcoal. Unfortunately, the heat released by the bagasse charcoal did not compare favorably with that of the wood charcoal, failing to raise 1 L of water to boiling while the wood charcoal raised the water to boiling for 25 minutes. Since the bagasse charcoal performed similarly to Kingsford brand charcoal, the emissions released were compared between these two fuels. Based on their averages, the bagasse charcoal emitted 1.4 times more CO, 1.6 times more SO₂ and 2.3 times more particulates but only 17% of the NOx emitted by Kingsford. / by Andrés Ramírez. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 86-90). / Reverse osmosis (RO) is a well-known process for desalinating seawater and brackish groundwater. Desalination is energy-intensive, so using photovoltaic (PV) panels to power the process is an attractive environmentally friendly concept, especially for community-scale systems. Increasing the system efficiency will lower the total cost of water produced, making the systems more economically competitive for a greater number of geographic locations. The thermal behaviors of PV panels and RO systems are complementary and can be exploited to improve photovoltaic reverse osmosis (PVRO) system efficiency. For a given level of solar radiation, a PV panel produces more electrical power at lower panel temperatures. For a given applied pressure, the flow of clean water across an RO membrane increases with increasing temperature. By using the RO feed water to cool the PV panels and warming the water in the process, more electrical power can be produced and higher flow rates of clean water across the RO membrane can be achieved, increasing total daily water production. The ability to cool the PV panels permits the use of low-cost, flat-plate concentrating mirrors, which further increase electrical power and clean water production. This thesis develops a thermal management system to improve the performance of a small-scale PVRO. Preliminary case studies show that the thermal exploitation concept is feasible and that a 50% increase in the total daily clean water production of a PVRO system is achievable, with an active thermal controller. A thermal controller is proposed that optimizes the PVRO system performance by minimizing the temperature of the solar panel and maximizing the temperature of the RO feed water. The control system uses a solar panel-mounted heat exchanger, circulator pump and servo valves to maximize water production while operating within the temperature limits of both the solar panel and the reverse osmosis membrane. Preliminary controller simulations show that it can successfully manage the temperatures of both the solar panel and RO feed water. The thermal management concept was experimentally validated on a small-scale, 300 L/day PVRO system. A 57% increase in clean water production was achieved using thermal management and solar concentrating mirrors, which agrees well with simulated performance predictions. / by Leah C. Kelley. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (p. 110-111). / by Tang Yew Tan. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2002. / Includes bibliographical references (p. 115-120). / by Ryan D. Welsh. / S.M.