Rafał Andrzejczyk

Analytical Model With Nonadiabatic Effects for Pressure Drop and Heat Transfer During Boiling and Condensation Flows in Conventional Channels and Minichannels

In this paper a method developed earlier by the authors is applied to calculations of pressure drop and heat transfer coefficient for boiling flow and condensation flow with account of nonadiabatic effects for some recent data collected from the literature. The first effect, the modification of interface shear stresses in an annular flow pattern, is considered through incorporation of the so-called “blowing parameter.” The mechanism of modification of shear stresses at the vapor–liquid interface for such case is presented in detail in the paper. In the case of annular flow it contributes to thickening and thinning of the liquid film, which correspond to condensation and boiling, respectively. There is also another influence of the wall heat flux, where it is influencing the bubble nucleation in the case of the bubbly flow pattern. As a result, a modified general form of the two-phase flow multiplier, applicable both to boiling flow and condensation flow, is obtained, in which the nonadiabatic effects are clearly pronounced. The obtained model of the two-phase multiplier, incorporating the nonadiabatic effects, is additionally used in predictions of the heat transfer coefficient.

Wpływ właściwości czynników chłodniczych na straty egzergii w pompie ciepła

Artykul poświecony jest wplywowi wystepujących w pompie ciepla strat egzergii na jej efektywnośc energetyczną, a co za tym idzie koszty funkcjonowania instalacji. Autorzy prezentują tu metodologie obliczeniową, ktora moze byc zastosowana w procesach projektowania ukladow cieplno-przeplywowych. Obliczenia zostaly wykonane na podstawie typowego ukladu powietrznej pompy ciepla pracującej w klimacie środkowo-europejskim. Ponadto w artykule wykonano analize techniczno-ekonomiczną pompy ciepla z wykorzystaniem wybranych czynnikow roboczych, ktore mogą byc stosowane w przyszlości.