Showing papers in "Engineering Letters in 2010"

The effect of temperature nonuniformities on transient behaviour of three-fluid crossflow heat exchanger

Abstract: A transient temperature response of three-fluid heat exchangers with finite core capacitance of the separating sheets is investigated numerically for the effect of temperature nonuniformity. Step perturbation is provided in the central (hot) fluid inlet temperature. The responses are found dependent on the nonuniformities present in the inlet temperature. Index Terms — finite difference, temperature nonuniformity, three-fluid heat exchanger, transient behaviour.

Characterization of JP-8/SiO2 and RP-1/SiO2Gels

Abstract: For next generation air-breathing and rocket propulsion systems gelled propellants can be a promising replacement for conventional solid and liquid propellants. Especially for rocket engine operation, the application of a gelled fuel and gelled oxidizer can combine the advantages of conventional solid and liquid propellants without taking into account the specific disadvantages of both individual systems. The present publication describes the rheological behavior of gelled JP-8 turbine fuel and gelled rocket propellant RP-1 when fumed silica is used as a gelling agent. Alongside the determination of an optimal gel mixing process, gel stability and rheological parameters showed a significant influence of the added silica amount.

Improvement of Microstructure and Fractured Property of Poly(L-lactic acid) and Poly(butylene succinate-co-e-caprolactone) Blend Compatibilized with Lysine Triisocyanate

Abstract: Blends of poly(L-lactic acid) (PLLA) and poly(butylene succinate-co-e-caprolactone) (PBSC) with and without addition of lysine triisocyanate (LTI) were prepared by using a conventional melt-mixer. The effect of LTI on the microstructures and fractured property of the blends was characterized by Fourier transform infrared (FT-IR) analysis and field emission scanning electron microscopy (FE-SEM). J-integral at crack initiation, Jin, and the total fracture energy, Jf, were measured as mode I fracture properties to assess the effect of LTI addition on these properties. Fracture morphologies were also examined by FE-SEM to characterize the effect of structural change due to LTI addition on the fracture micromechanism. It was found that LTI addition dramatically improves the compatibility between PLLA and PBSC and results in the improvement of the fractured energy, Jf of ACI value was about 17 times larger than that of neat PLLA. FE-SEM also showed that the reduction of the phase-separation increases local ductile deformation in the crack-tip region.

Experimental Investigation of Sagging and Ballooning in LOCA for Indian PHWR

Abstract: In a nuclear reactor Loss of Coolant acci- dent (LOCA) considers wide range of postulated dam- age or rupture of pipe in the heat transport piping system. In the case of LOCA with/without failure of emergency core cooling system in a Pressurised Heavy Water Reactor (PHWR), the Pressure Tube (PT) temperature could rise significantly due to fuel heat up and gross mismatch of the heat generation and heat removal in the affected channel. The extent and nature of deformation is important from reactor safety point of view. Experimental set-ups have been designed and fabricated to simulate sagging (down- ward deformation) and ballooning (radial deforma- tion) of PT for 220 MWe Indian PHWRs. It is ob- served that sagging initiates at a temperature around 450 ◦ C. Contact between PT and Calandria Tube (CT) occurs at around 585 ◦ C. At 60 bar internal pressure and initial heat up rate of 2.37 ◦ C/sec, ballooning of PT initiates at a temperature around 520 ◦ C. The PT- CT contact is found to take place at 640 ◦ C temper- ature. The structural integrity of PT is retained (no breach) for all the experiments. The PT heatup is found to be arrested after the contact between PT and CT, thus establishing moderator acting as an ef- ficient heat sink for IPHWRs.