Two-phase thermosyphon heat exchanger : application possibilities

W pracy przedstawiono oryginalną konstrukcję dwufazowego, termosyfonowego wymiennika ciepła (DTWC), który składa się z dwóch poziomych, cylindrycznych zbiorników umieszczonych jeden nad drugim, połączonych ze sobą króćcami. W płaszczu dolnym umieszczony jest pęk rur, na którym zachodzi wrzenie, natomiast w płaszczu górnym pęk, na którym ciecz robocza się skrapla. Ustalono, że zastosowanie rurek z powłoką porowatą powodowało polepszenie charakterystyk cieplnych DTWC. Zaobserwowano, że średni współczynnik przejmowania ciepła dla parownika bardzo mocno zależy od początkowego poziomu cieczy roboczej. Do szacowania strumienia ciepła przenoszonego w prototypowym DTWC zaproponowano zmodyfikowany wzór Pec/eta. Przedstawiono kilka możliwości zastosowania prototypowego DTWC w układach przemysłowych.A special design of two-phase thermosyphon heat exchanger (TPhTHEx) is proposed. The prototype heat exchanger consists of two horizontal cylindrical vessels connected with two risers and a downcomer. The obtained results indicated a better performance of TPhTHEx with evaporator bundle built of porous coated tubes than corrugated and smooth tubes. It was observed that the evaporation heat transfer coefficient was strongly influenced by the initial liquid level above the top tube row. The modified Peclet equation was proposed for calculation of heat flux transferred in TPhTHEx. Potential applications of the proposed prototype TPTHEx include vaporization of li-quids at low temperatures and heat recovery from sewage or exhaust gases

Heat transfer in plate heat exchanger channels: Experimental validation of selected correlation equations

This study is focused on experimental investigation of selected type of brazed plate heat exchanger (PHEx). The Wilson plot approach was applied in order to estimate heat transfer coefficients for the PHEx passages. The main aim of the paper was to experimentally check ability of several correlations published in the literature to predict heat transfer coefficients by comparison experimentally obtained data with appropriate predictions. The results obtained revealed that Hausen and Dittus-Boelter correlations underestimated heat transfer coefficient for the tested PHEx by an order of magnitude. The Aspen Plate code overestimated heat transfer coefficient by about 50%, while Muley-Manglik correlation overestimated it from 1% to 25%, dependent on the value of Reynolds number and hot or cold liquid side

In vitro morphogenic events in culture of Lotus corniculatus L. seedling root explants

The experiments were carried out on Lotus corniculatus (L.) seedling root explants of the cultivar varieties Skrzeszowicka, Caroll A10 and strain 175. Callus formation and shoot regeneration were the major explant response depended mainly on of the studied genotype and used plant growth regulators (PGRs). Primary cortex of proximal and distal end of explant was the most active tissue for callus proliferation. For shoot primordia differentiation deeper zones of cortex took a part. The process of meristematic centre initiation was not uniform and various level of shoot differentiation events were observed not earlier than 3 weeks of culture. Usually, the shoot primordia regeneration began on proximal rather than distal end of the explant. BAP rather than urea derivatives stimulated shoot proliferation in extended cultures. Increasing of BAP and TDZ concentrations brought about the explant polarity and expansion of the meristematic zones. The explant position in root did not have significant influence on the number of regenerated shoots. The cultures only had better bud formation by TDZ when compared to BAP. BAP stimulated bud formation and development of the shoots from them. Short term of TDZ treatment of explants stimulated meristem formation which developed into buds and shoots. CPPU stimulated callus proliferation and bud formation when explants pretreatment was prolonged from 12 to 36 hrs