Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Powiadomienia systemowe

Sesja wygasła!

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: artificial

Sortuj według:

Ogranicz wyniki do:

Effect of artificial coarseness on the performance of rectangular solar air heater duct: a comparative study

Dubey Manoj Kumar, Prakash Om

Archives of Thermodynamics

2023

Vol. 44, no 3

325--358

Solar air heater is regarded as the most common and popular solar thermal system and has a wide range of applications, from residential to industrial. Solar air heater is not viable because of the low convective heat transfer coefficient at the absorber plate which contributes to decreasing the thermal efficiency. Artificial coarseness on the plain surface is the most effective method to enhance heat transfer with a moderate rate of friction factor of flowing air in the design of solar air heater duct. The different parameters and different artificial coarseness are responsible to alter the flow structure and heat transfer rate. Over the years different artificial roughness and how its geometry affects the performance of solar air heater have been thoroughly studied. Various investigators report the correlations between heat transfer and friction factors. In the present study, a comparison of several artificial coarseness geometries and methods with a view to enhancing the performance of solar air heater has been made. A brief outline has also been presented for future research.

Stochastyczne, nieizotermiczne smarowanie stawu biodrowego z odkształcalną chrząstką

Wierzcholski K.

Tribologia

2005

nr 4

309-322

W niniejszej pracy przedstawiono metodę rozwiązywania problemu nieizotermicznego smarowania naturalnych stawów biodrowych oraz endoprotez z uwzględnieniem deformacji powierzchni stawowych oraz związanych z tym faktem efektów losowych. Przedstawiono również wyniki pomiarów powierzchni głów kostnych na aparacie Rank Taylor Hobson-Talyscan 150. Uzyskane wyniki doświadczalne zostały opracowane z użyciem programu komputerowego TALYMAP Expert oraz Microsoft Excel.

The determination of hydrodynamic lubrication of artificial metal endoprothesis and the elastohydrodynamic lubrication of articular human hip joints, leads to the precise analysis of irregularities and inequalities of joint cooperating surfaces with exactness of one micrometer or even more than one micrometer for the boundary friction. The measurements of the bone head surfaces are performed by micro sensor laser installed in the Rank Taylor Hobson-Talyscan 150 Apparatus and then elaborated by means of the TALYMAP Expert and Microsoft Excel Computer Program. From 29 measured samples the following statistical parameters St, Sz, Sa are calculated: St, Sz, Sa of surface roughness expressed in micrometers. Cooperating surfaces of human hip joint are coated by the hyaline, non-transparent, damp and rough cartilage with hyper elastic properties [1],[2]. The gap height between cooperating surfaces of human joints has value from 60 to 200 microns. According to this fact the inequalities with depth about some microns have important meaning during the elasto-hydrodynamic lubrication. The earliest visible sign of osteoarthritis is localized fibrillation or disruption of the most superficial layers of the articular cartilage (see Fig.1 and Fig.2). As the disease progresses, more of the articular surface becomes roughened and irregular, and fibrillation extends deeper into the cartilage until it reaches subchondral bone. As the cartilage fissures grow deeper, the superficial tips of the fibrillated cartilage tear, releasing free fragments into the joint space and decreasing the cartilage thickness. At the same time, enzymatic degradation of matrix may further decrease the cartilage volume. On the ground of performed measurements it is easy to see that the asperities of the artificial joint surfaces are more smaller than asperities occurring in articular bone surfaces of human hip joints.