Combination of two physical phenomena, capillary pressure gradient and wettability gradient, allows a simple two-step fabrication process that yields a reliable hydrophobic self-cleaning condenser surface. The surface is fabricated with specific microscopic topography and further treatment with a chemically inert low-surface-energy material. This process does not require growth of nanofeatures ...

Split air conditioning units are usually used for small and medium scale residential buildings. Therefore, more energy efficiency and lower cost are needed along with reliable control for the air conditioning units. An experimental investigation has been carried out to study the performance of a direct expansion air conditioning (A/C) unit having a variable speed condenser fan. The modulation o...

Polymer electrolyte membrane (PEM) fuel cells are highly efficient energy converters and provide electrical energy, cathode exhaust gas with low oxygen content, water and heat. Recently, fuel cells have been investigated for the use on aircraft where they have the potential of replacing the auxiliary power units (APU) that are currently used for generating electrical power during ground operati...

Preface In the scope of my studies at the Technical University of Denmark (DTU) in the Engineering Acoustics master program, I have done my final project about modelling distortion in condenser microphones. This subject was originally proposed by Brüel & Kjaer Sound & Vibration Measurement A/S (B&K) under the title Distortion process in condenser microphones. In February 2009 I have started my ...

Microchannel heat exchangers (MCHX) are being increasingly applied in heat pumps because of their compactness, significant charge reduction, lower refrigerant pressure drop and lower air-side fan power consumption compared to traditional round tube-plate fin (RTPF) heat exchangers. Using a microchannel condenser as well as evaporator in a heat pump system also offers significant potential for c...

A numerical simulation of a liquid overfeed system working with pure refrigerants in steady state conditions has been performed. The global algorithm is based on the sequential resolution of the different elements of the system (compressor, evaporator, condenser, ... ). For each element, a simplified mathematical model based on global balances of mass, momentum and energy is used. For the evapo...