Saturated Hot Water Research Articles

Durability of chemically modified sisal fibre in cement-based composites

The degradation of sisal fibre in a cement-based matrix due to the highly alkaline environment reduces the strength of the composite. In this research, to avert this degradation, alkaline treatment and acetylation were respectively performed with sodium hydroxide (NaOH) and Acetic Acid or Acetic Anhydride to improve the resistance of the fibre to alkaline attack. In addition, single fibre pull-out (SFP) tests were performed to evaluate the influence of chemical treatment on fibre strength, fibre-matrix interaction and also determine the critical fibre length. Specimens were tested in indirect tension (flexure) at 28 days to determine the strength of the composite. Additional ageing tests by extended curing in water at 24 °C, lime saturated hot water at 70 °C, and alternate cycles of wetting and drying were done. Aged samples were further tested at 90 days to evaluate the durability of the fibre. It was found that a combination of alkali treatment and acetylation was the most effective treatment condition, followed by that of alkali treatment at low concentrations of sodium hydroxide. At higher concentrations of sodium hydroxide, a significant reduction in strength was observed. Chemical treatment improves the durability of sisal fibres in concrete, albeit slight degradation still occurs.

Fatigue Fracture Features of Pressure Vessel Steel in Simulated Light Water Reactor Environment

To evaluate fatigue crack growth of reactor pressure vessel steel at reactor operating conditions, tests were performed in air saturated hot water. The main test parameter was a loading frequency. Crack growth rate was increased with decreasing frequency up to a critical value. It was assumed through fractographic study and surface analysis that the enhancement of crack growth rate was environmentally assisted due to hydrogen embrittlement. In the low stress intensity factor range, cracks grew through crystallographic facets and tear ridges. Moreover, cleavage occurred at MnS inclusions. Larger cleavage occurred near MnS inclusions in the high stress intensity factor range. Brittle facets combined with voids and stair or step-like cracks with arrest marks appeared at sites some distance from the MnS inclusions. It was suggested that the environmentally assisted cracks were related to interactions of hydrogen with oxide film and also to dislocation motion at the crack tip.

Strain Rate Effects on the Fatigue Crack Growth of SA508 Cl.3 Reactor Pressure Vessel Steel in High-Temperature Water Environment

Corrosion fatigue tests were performed in air saturated hot water to assess fatigue crack growth behavior of reactor pressure vessel steel at the LWR operating condition. The main test parameter was loading frequency. Crack growth rate was increased with decreasing frequency until a critical frequency. It was found through fractographic study that the enhancement of crack growth rate was environmentally assisted by the hydrogen embrittlement, since brittle striations and cleavagelike facets with microvoid were formed in the crack growth process. The strain rate effects on crack growth rate were investigated through da/dt versus dε/dt curves. At intermediate range, there is a transient point which corresponds to an onset of dynamic strain aging and abruptly increases the crack growth rate; above the transient point, small-size-particle-enhanced brittle cracks, while only large-size-particle-enhanced brittle cracks before the transient. From the fractography, it is suggested that EAC may be enhanced by specific strain rate, and that EAC may be related to interactions of hydrogen with oxide film and to Luders band movement with a high strain gradient at inclusion/matrix interface.

Performance of stationary blade cascade for two-phase flow of saturated hot water.

The geometry of blades and cascades for a single-component, two-phase flow with a high void ratio was optimized to design an axial-impulse-type two-phase flow turbine suitable for recovering geothermal and/or industrial waste heat. The dissimillar performances of scaled cascades as well as the strong dependence of a cascade's performance on vapor density were predicted by a simple theoretical model. These were confirmed by the measured thrust conversion efficiency of a blade cascade located within a two-phase jet emerging from a nozzle. The nozzle expands the hot, saturated water at 510 K into a chamber where the pressure varies between 15 kPa and 0.45 MPa.

Cycle performance of total flow turbine systems. 1st Report. Utilization of saturated hot water.

From the viewpoint of energy saving and the development of new energy resources, it is important to utilize water-dominated geothermal resources and waste-heat sources from factories. As systems utilizing such resources, steam flashing system, binary-fluid systems, and total flow turbine systems are considered for power generation. In this study, thermodynamic consideration on such systems as single and double total flow turbine systems (1 TS, 2 TS) is made under the condition of saturated hot water at the inlet of the systems, compared with single flash turbine systems (1 FS). First, the available energy of 1 TS and 2 TS is explained graphically on a T-S diagram, and an optimum intermediate temperature in 2 TS, which maximizes the system efficiency, is given. Second, the superiority of total flow system efficiency to that of 1 FS is clarified and the magnitude of the improvement is estimated. Furthermore, the effects of each factor on the cycle performance of 1 TS and 2 TS are shown.

Large energy storage systems for utilities

In addition to the capacity on line, electric networks usually need 8–10 per cent of their installed capacity readily available to handle load variations. Thermal storage of energy as pressurised saturated hot water has done this job for years, but only on a small scale because of cost limitation of the steel pressure vessel. This paper shows that steel lined cavities deep underground, using the rock to provide containment, are economical and practical in large capacities for this energy storage. By reducing the cavity pressure, steam is flashed from the hot water and used to drive peaking turbines when needed; at low load periods surplus steam is condensed in the water to recharge the vault. The saturation pressure of the hot water is borne by the overburden pressure of the rock formation in which the storage vault is prepared. At usual steam plant saturation temperatures the effective storage density is in the range of 18–21 electric kWh/m 3 of storage volume, which is 20–50 times the capacity of the usual pumped hydro systems. Recovery of stored energy ranges from 75–90 per cent. The cost of a facility to deliver 1000 MW of peaking power for 10 h would fall in the range of $250–350 million, including indirect costs, interest, etc. The underground facilities represent about 40 per cent of the cost: the balance is for conventional generating and steam plant equipment.