Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2003. / Thesis advisor(s): Knox T. Millsaps, Jr. Includes bibliographical references (p. 49-50). Also available online.

No description available.

No description available.

This experim ental project aims to describe the influencing factors in the vacuum boiling o f w ater in w ater vapour refrigeration system s Testing was conducted using a 2 kW three-stage steam je t ejector system, w ith barom etric condensers, as the com pression device. Three direct-contact evaporators were used to investigate the boiling phenom ena. T hese were : a through-flow evaporator w here heal and mass transfer rates were established for boiling m echanism s at various positions within the evaporator; a vertical cylinder where small quantities o f w ater were subjected to rapid decom pression and the effects m easured, and a sim ple channel for photographic studies o f the process. Boiling in direct-contact water vapour systems is described herein The vacuum boiling proo ss was found to be controlled by a com bination o f the w ater surface tem perature and the hydrostatic pressure gradient, these being governed by the w ater vapour flow geometry between the w ater surface and ejector suction and convective heat transfer below the boiling region. The contributions o f the various boiling regim es to the total heat transfer are discussed. Heat and mass transfer coefficients and their applicability to evaporator design are presented

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Dr. Yogendra Joshi; Committee Member: Dr. S. Mostafa Ghiaasiaan; Committee Member: Dr. Sheldon Jeter. Part of the SMARTech Electronic Thesis and Dissertation Collection.

In this study a semi-passive pulse thermal loop (PTL) was designed and experimentally validated. It provides improved heat transfer over passive systems such as the loop heat pipe in the moderate to high heat flux range and can be a sustainable alternative to active systems as it does not require an electric pump. This work details the components of the engineering prototype and characterizes their performance through the application of compressible and two-phase flow theory. A custom LabVIEW application was utilized for data acquisition and control. During operation with refrigerant R-134a the system was shown to be robust under a range of heat loads from 100 W to 800 W. Operation was achieved with driving pressure differentials ranging from 3 bar to 12 bar and pulse frequencies ranging from 0.42 Hz to 0.08 Hz. A smaller pressure differential and an increased pulse frequency results in improved heat transfer at the boilers. An evolution of the PTL is proposed that incorporates a novel, ejector-based pump-free refrigeration system. The design of the pulse refrigeration system (PRS) features valves at the outlet of two PTL-like boilers that are alternately actuated to direct pulses of refrigerant through an ejector. This is intended to entrain and raise the pressure of a secondary stream of refrigerant from the cooling loop, thereby replacing the compressor in a conventional vapor-compression cycle. The PRS is therefore characterized by transient flow through the ejector. An experimental prototype has been constructed which is able to operate as a conventional PTL when the cooling section is bypassed, although full operation of the refrigeration loop remains to be demonstrated. The design of the ejector is carried out using a one-dimensional model implemented in MATLAB that accounts for compressibility effects with NIST REFPROP vapor data sub-routines. The model enables the analysis of ejector performance in response to a transient pressure wave at the primary inlet. The high driving pressures provided by the PTL permit operation in a micro-gravity environment with minimal power consumption. Like the PTL, the proposed PRS is therefore well suited to terrestrial and aerospace applications where it could be driven by waste heat from electronics or solar thermal energy. As a novel semi-passive thermal management system, it will require complex control of the valves. Further analysis of the transient thermodynamic cycle is necessary in order to characterize and effect successful operation of the PRS. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2013.

The purpose of this thesis is to examine possible waste heat recovery methods in data centers. Predictions indicate that in the next decade data center racks may dissipate 70kW of heat, up from the current levels of 10-15kW. Due to this increase, solutions must be found to increase the efficiency of data center cooling. This thesis will examine possible waste heat recovery technologies which will improve energy efficiency. Possible approaches include phase change materials, thermoelectrics, thermomagnetics, vapor compression cycles, absorbtion and adsorbtion systems. After a thorough evaluation of the possible waste heat engines, the use of an ejector heat pump was evaluated in detail. The principle behind an ejector heat pump is very similar to a vapor compression cycle. However, the compressor is replaced with a pump, boiler and an ejector. These three components require less moving parts and are more cost effective then a comparable compressor, despite a lower efficiency. This system will be examined under general operating conditions in a data center. The heat load is around 15-20kW and air temperatures near 85°C. A parametric study is conducted to determine the viability and cost effectiveness of this system in the data center. Included will be various environmentally friendly working fluids that satisfy the low temperature ranges found in a data center. It is determined that Ammonia presents the best option as a working fluid for this application. Using this system a Coefficient Of Performance of 1.538 at 50°C can be realized. This will result in an estimated 373,000 kW-hr saved over a year and a $36,425 reduction in annual cost. Finally, recommendations for implementation are considered to allow for future design and testing of this viable waste heat recovery device.