Zero-degree calorimeters have limited space and extreme levels of radiation. A simple, low cost, radiation hard design uses tungsten metal as the absorber and a suitable liquid as the Čerenkov radiator. In other applications a PPAC (Parallel Plate Avalanche Counter) operating with a suitable atmosphericpressure gas is an attractive active material for a calorimeter. It can be made radiation har...

Experimental determination of void fraction in two-phase flows can be achieved in a number of different ways, including: the quick closing of valves at each end of a test section, impedance measurement techniques, gamma or x-ray absorption, and analysis of visualization results. This paper presents a method of determining void fraction in separated, two-phase refrigerant flows through analysis ...

Refrigerant mass migration and redistribution have been regarded as factors influencing the performance of air conditioning and refrigeration systems. This paper presents a dynamic model of an R134a automotive A/C system that is able to capture the shut-down and start-up cycling dynamics including the refrigerant mass migration transients. Building upon recent work (Li and Alleyne, 2010), the h...

A presentation of the design of the Organic Rankine cycle (ORC) with heat regeneration and superheating processes is a subject of this paper. The maximum temperature level in the ORC is considered to be 110°C and the maximum pressure varies up to 2.5MPa. The selection process of the appropriate working fluids, thermal design and calculation of the cycle and its components are described. With re...

Refrigerants that are used in refrigeration systems, cause environmental difficulties such as depletion of ozone layer and greenhouse effect. Thus, we must find substitutes for such refrigerants, in this paper, the effect of refrigerant on the thermodynamics performance of refrigeration cycles are studied. To do this, a refrigerator that has designed for R12, is simulated. Results show that pur...

Refrigerants that are used in refrigeration systems, cause environmental difficulties such as depletion of ozone layer and greenhouse effect. Thus, we must find substitutes for such refrigerants, in this paper, the effect of refrigerant on the thermodynamics performance of refrigeration cycles are studied. To do this, a refrigerator that has designed for R12, is simulated. Results show that pur...

A numerical model of subcritical and trans-critical power cycles using a fixed-flowrate low-temperature heat source has been validated and used to calculate the combinations of the maximum cycle pressure (Pev) and the difference between the source temperature and the maximum working fluid temperature (DT) which maximize the thermal efficiency (ηth) or minimize the non-dimensional exergy losses ...

This paper presents experimental techniques to determine the amount of lubricant in each of the major components of an R134a automotive A/C system using ND-8 (PAG 46) oil—compressor, condenser, liquid tube, evaporator and accumulator. Three different techniques are presented: Remove and weigh Flushing Mix and sample The advantages and disadvantages, as well as the suitability of each technique ...

A new dual-fluid concept was studied that could eventually find application for cold-gas propulsion for small space satellites or other constant flow applications. In basic form, the concept uses two different refrigerant working fluids, each having a different saturation vapor pressure. The higher vapor pressure refrigerant remains in the saturation phase and is used to pressurize the lower sa...

We describe a sensitive method for measuring time-dependent changes in refractive index within approximately 5 microm of an interface using off-null time-resolved ellipsometry and a dual-cavity femtosecond laser. The sensitivity to changes in refractive index is two orders of magnitude higher than conventional picosecond interferometry. A thin metal film on a sapphire substrate is heated by app...