Data are presented demonstrating a low thermal resistance lithographic laser. An 8 mm vertical-cavity surface emitting laser defined using lithography and epitaxial crystal growth provides output power of 14 mW, slope efficiency of 0.88 W/A corresponding to differential quantum efficiency of 70% and power conversion efficiency of 26%. Low thermal resistance, even without heatsinking, results in...

This paper describes the experimental efficiency of a compact organic Rankine cycle (ORC) system with a compact rotary-vane-type expander. The compact ORC system can be used for power generation from low-temperature heat sources such as waste heat from various small-scale heat engines, fuel cells, electric devices, and solar thermal energy. The purpose of this study is to develop an ORC system ...

Thermal efficiency is a common benchmark used to compare competing processes when a new LNG project is being developed. Often this type of comparison can be misleading when used in isolation because plant design premises are not consistent from project to project. Thermal efficiency depends on numerous issues such as gas composition, inlet pressure and temperature, and even more obscure issues ...

The paper presents preliminary results of an experimental study on solar water heater with full width and 75% twisted tapes as heat transfer enhancement device. The study shows that the thermal efficiency due the use of the twisted tape increases by 4.5-8%; higher for the 75% twisted tape. Keyword Solar water heater (collector), tube-in-fin, twisted tape, thermal efficiency, performance enhance...

There can be a significant discrepancy between predicted and measured power conversion efficiency when using piezoelectric polymers for thermal energy harvesting. The influence of temperature and strain on electrical parameters can impact overall performances. We report the temperature and strain dependence of PVDF dielectric constant and losses and their impact on power conversion efficiency o...

Exponential fins are mathematically analyzed in this paper. Two types are considered: i straight exponential fins and ii pin exponential fins. The possibility of having increasing or decreasing cross-sectional areas is considered. Different thermal performance indicators are derived. The maximum ratio between the thermal efficiency of the exponential straight fin to that of the rectangular fin ...

Reliably routing heat to and from conversion materials is a daunting challenge for a variety of innovative energy technologies--from thermal solar to automotive waste heat recovery systems--whose efficiencies degrade due to massive thermomechanical stresses at interfaces. This problem may soon be addressed by adhesives based on vertically aligned carbon nanotubes, which promise the revolutionar...

− The concept of a durable development in the field of thermal energy supply of the localities implies the use of efficient technical solutions that are capable to ensure the fulfillment of their social needs in conditions of economic efficiency and energetic efficiency. Having as research base the centralized district heating of the Iasi city the research team proposes to resolve the control p...

One of the effective methods to improve the thermal efficiency of solar collectors is using nanofluids as the coolant. The present study experimentally investigated the effect of SiO2/water nanofluid with 1% mass fraction on the performance of a symmetric collector, i.e. conical solar collector. The conical solar collector with 1 m2 area and normal to the earth was tested in Ahvaz, a city in th...

Thermal efficiency of borehole heat exchangers (BHE) is of crucial importance for the design and optimization of ground source heat pump (GSHP) system. This paper investigates thermal efficiency of a BHE with three drillhole diameters: 121 mm, 165 mm and 180 mm. The BHE was installed in a GSHP system of an office building located in Nuremberg, Germany. Thermal properties and hydraulic propertie...