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Abstract:A solar driven cooling system consisting of a single effect H 2 O-LiBr absorbtion cooling module (ACS), a parabolic trough collector (PTC), and a storage tank (ST) module is analyzed during one full day operation. The pressurized water is used to transfer heat from PTC to ST and to feed the ACS desorber. The system is constrained to operate at the maximum ACS exergetic efficiency, under a time dependent cooling load computed on 15 July for a one storey house located near Bucharest, Romania. To set up the solar assembly, two commercial PTCs were selected, namely PT1-IST and PTC 1800 Solitem, and a single unit ST was initially considered. The mathematical model, relying on the energy balance equations, was coded under Engineering Equation Solver (EES) environment. The solar data were obtained from the Meteonorm database. The numerical simulations proved that the system cannot cover the imposed cooling load all day long, due to the large variation of water temperature inside the ST. By splitting the ST into two units, the results revealed that the PT1-IST collector only drives the ACS between 9 am and 4:30 pm, while the PTC 1800 one covers the entire cooling period (9 am-6 pm) for optimum ST capacities of 90 kg/90 kg and 90 kg/140 kg, respectively.

The pneumatic elastic elements are widely used in the secondary suspension of modern railway vehicles due to their important advantages compared to the conventional ones. In the present paper, the modelling and analysis of the pneumatic suspension is approached, taking into account the main elements, pneumatic enclosures and rubber elements. The analysis performed investigates the influence of relevant parameters on suspension stiffness and on its dynamic response.

Abstract. The aim of the present paper is to identify total time on test (TTT) estimators which require only partial information on sampling units. This allows an important simplification of the testing or observation procedure. The approach is based on the division of the testing/observation period into intervals so that TTT estimators to be determined using only classes numerical attributes. Division is made based either on failure rank or on time. A case study based on real field empirical data is carried out in order to assess the effectiveness of TTT estimators.

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