Absorption heat pump for space applications

In the first part, the performance of the Absorption Heat Pump (AHP) with water-sulfuric acid and water-magnesium chloride as two new refrigerant-absorbent fluid pairs was investigated. A model was proposed for the analysis of the new working pairs in a heat pump system, subject to different temperature lifts. Computer codes were developed to calculate the Coefficient of Performance (COP) of the system with the thermodynamic properties of the working fluids obtained from the literature. The study shows the potential of water-sulfuric acid as a satisfactory replacement for water-lithium bromide in the targeted temperature range. The performance of the AHP using water-magnesium chloride as refrigerant-absorbent pair does not compare well with those obtained using water-lithium bromide. The second part concentrated on the design and testing of a simple ElectroHydrodynamic (EHD) Pump. A theoretical design model based on continuum electromechanics was analyzed to predict the performance characteristics of the EHD pump to circulate the fluid in the absorption heat pump. A numerical method of solving the governing equations was established to predict the velocity profile, pressure - flow rate relationship and efficiency of the pump. The predicted operational characteristics of the EHD pump is comparable to that of turbomachinery hardware; however, the overall efficiency of the electromagnetic pump is much lower. An experimental investigation to verify the numerical results was conducted. The pressure - flow rate performance characteristics and overall efficiency of the pump obtained experimentally agree well with the theoretical model

Correlations for wall heat flux partitioning during subcooled forced flow film boiling

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.vk201

A Framework for Spectrally Efficient Noncoherent Communication

76 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2000.This thesis considers noncoherent communication over a frequency-nonselective channel in which the time-varying channel gain is unknown a priori , but is approximately constant over a coherence interval . Unless the coherence interval is large, coherent communication, which requires explicit channel estimation and tracking prior to detection, incurs training overhead which may be excessive, especially for multiple antenna communication. In contrast, noncoherent detection, which may be viewed as a generalized likelihood ratio test (GLRT) for joint channel and data estimation, does not require separate training. The goal of this thesis is to provide a framework for designing spectrally efficient noncoherent communication systems, analogous to the wealth of signal and code design techniques available for coherent communication. The main results are as follows: (1) A "signal space" criterion is developed for signal and code design for noncoherent communication, in terms of the distances of signal points from the decision boundaries. (2) The noncoherent metric thus obtained is used to guide the design of signals for noncoherent communication that are based on amplitude/phase constellations. These are significantly more efficient than conventional differential phase shift keying (PSK), especially at high signal-to-noise ratio (SNR). Also, known results on the high SNR performance of multiple symbol demodulation of differential PSK are easily inferred from the noncoherent metric. (3) The GLRT interpretation is used to obtain a linear complexity (in the block length) implementation of multiple symbol demodulation of differential PSK. The degradation of this scheme from the exact, exponential complexity, implementation can be made as small as desired. (4) A block transformation is demonstrated to produce noncoherent space-time codes with full diversity, starting from an appropriately chosen single antenna noncoherent code. This provides a constructive approach for obtaining high rate noncoherent space-time codes for large coherence intervals. Previous optimization approaches to finding noncoherent space-time codes would be difficult to implement in such a setting, since they involve a search over a space whose dimensions grow exponentially with the block length and the code rate.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD