[en] In the 1970s VGB member undertakings designed and put into operation a number of large cooling systems. Experience from these has served to perfect the drafts of the cooling water guidelines. It has been shown that, for example, the use of corrosion-resistant materials, such as stainless steel or titanium, as the heat transfer tube material subjected to saliferous cooling water, helps to increase the availability and economic operation of a power station. The positive experience which has been gained from balance-closed intermediate cooling systems and desalted cooling water has led to the recommendation of this solution for power station operation. (orig.)

[en] A cryocooler has been developed that uses a unique refrigerant in a throttle cycle to achieve temperatures below the normal boiling point of liquid nitrogen. 70 K was achieved at no load condition and continuous operation with a 1.5 W heat load below 77 K has been demonstrated. The refrigerator consists of a compressor package that is similar to a standard air conditioning system, a cold end which has no moving parts that consists of a heat exchanger with a cold plate, and two gas lines connecting the compressor and the cold end. The system requires no maintenance. Several prototypes have been built, tested and delivered to a customer for application in the field of high temperature superconducting filters for cellular phone communications. The cold end has the design flexibility to be customized for different applications. System performance can also be customized by designing different refrigerants that can be used without the need to modify the hardware

[en] High efficiencies can be achieved in the conversion of heat into electrical energy by the introduction of a combined magnetohydrodynamic (MHD) steam cycle. The potential offered by MHD has been demonstrated by studies showing coal-to-busbar conversion efficiencies approaching 50% with an electricity cost lower than that of competitive systems. Low NOsub(x) and SO₂ emission levels are obtained. The development program in the world will be described briefly, problem areas identified and recommendations for new developments given. (orig.)

[en] Terminal temperature difference (TTD) and the drains cooler approach (DCA), the thermal performance parameters for closed feedwater heaters, (CFWH) in steam power cycles, frequently are selected on the basis of economics. In the design study process, optimal heater performance is determined by analyzing the trends in overall cycle performance economics as they vary with heater TTD and DCA. TTD and DCA are selected to provide the lowest evaluated cost, taking into account unit performance cost and the investment costs associated with the heaters as these performance parameters are varied. Practical constraints such as an overall heater length, tube side velocities, desuperheating (DSH) zone wet wall, etc, must be considered as well. An exception occurs when this procedure is applied to the TTD of the highest pressure heater in the cycle. When calculating overall cycle performance, the heat rate is found to improve with improved (lower) TTD results in greater investment costs, the evaluation for the highest extraction pressure CFWH may be contrary to those obtained for similar calculations on other heaters. This paper discusses guidelines for calculating heater performance parameters and specifically addresses the practical aspects of choosing the TTD's for CFWH in a steam power cycle

[en] The inherent numerical properties of large thermal-hydraulic system codes may be usually verified by means of simpler codes, dealing with selected cases of restricted practical application. The problem considered was the single-phase, natural circulation flow in a simple loop, under unstable flow conditions. Neutral stability curves were derived for the system and effect of nodes number in the expected system behavior analyzed. The codes developed in a previous work have been further refined to analyze the problem under two approaches: nodal one, based on a finite-difference approximation and a modal one, based in a modal decomposition of the governing equations in Fourier series. Theoretical values for the steady state parameters are obtained for both approximations. The nodal code was used as the standard approximation and different schemes or different order have been used. The modal code, with the modes number ranging from 30 to 100, was used as an free approximation of numerical diffusion. In this case, the energy equation was solved considering also a constant diffusion term, allowing a partial simulation of the nodal approximation numerical diffusion. Results show that the inclusion of this diffusion reasonably accounts for the solution damping, allowing a qualitative recovering of the nodal behavior. System non-linearity naturally precludes the exact coincidence of the obtained results. A similar analysis may be used to assess the effect of a given discretization nodes number on the dynamics of more complex thermal-hydraulic systems. (author). 6 refs., 4 figs

[en] Analyses of a high interaction closed cycle MHD generator have been performed to confirm the feasibility of the fully ionized seed concept. The results show that fully ionized seed can be realized in a full scale generator and that it has an advantage over partially ionized seed of higher adiabatic efficiency. In order to keep the plasma in a given generator stable, the results show that the seed fraction and the external load fluctuation must stay within +- 5% and +- 3%, respectively. For a wider change in the external load we can also keep the plasma stable if the change is so slow that we can adjust the magnetic field, the thermal input and the working gas pressure. (author)

[en] In this paper, several definitions of energy and exergy efficiency for closed systems for thermal energy storage (TES) are developed and discussed. A simple model is utilized in which heat quantities are transferred at specified temperatures to and from a TES. Efficiency definitions are considered for the overall storage process and for the three component periods which comprise a complete storage process (charging, storing, and discharging). It is found that appropriate forms for both energy and exergy efficiency definitions depend on which quantities are considered to be products and inputs; different efficiency definitions are appropriate in different applications; comparisons of different TES systems can only yield logical results it they are based on a common definition, regardless of whether energy or exergy quantities are considered; and exergy efficiencies are generally more meaningful and illuminating than energy efficiencies for evaluating and comparing TES systems. A realistic, but simplified, illustrative example is presented. The efficiency definitions should prove useful in the development of valid and generally accepted standards for the evaluation and comparison of different TES systems

[en] The study of unusual plate shapes in orifice plate type flowmeters is presented, with a view to providing data for the substitution of the plate with one centered circular orifice in those applications where its use is not possible. For this purpose, six pairs of plates with different forms, with and without chamfered edges, were made and tested in a closed water loop. Results show that, generally, the use of chamfers improves the results and, in the case of perforated and slotlike orificed plates, the narrow-ness of the fluid passage tends to make unnecessary its use. (Author)

[en] Development of the design of cooling towers and recirculated cooling water systems at the Industrial Design Co. (IPARTERV). Cooling technological elements, drift eliminators, water distribution systems, water spray equipments, packings. Building technology, building constructions. Reconstruction of cooling towers. Desirable future of the power economy

[en] The onset of the nonequilibrium conductivity in a closed-cycle MHD generator is experimentally investigated. Conditions for deviations from a Maxwellian electron energy distribution are realized during an afterglow experiment. Here, values of the electron temperature and electron density correspond with those present at the entrance of an MHD generator working at low stagnation temperatures (TS less than or equal to 2000 K). Minimum currents are measured in MHD experiments. They correspond to the threshold values of the electron density (5 x 10 to the 18th per cu m) for the transition from a non-Maxwellian to a Maxwellian shape of the electron energy distribution. For low inlet electron densities (less than or equal to the threshold value) the onset of the nonequilibrium conductivity becomes difficult and relaxation ionization lengths up to the generator length have been shown to exist by the experiments. At low stagnation temperatures, higher inlet values of electron density and shorter relaxation lengths are realized by means of preionization. 12 references