Wyniki wyszukiwania - BazTech

1

Enhancing Thermal Performance of Hot Storage Tanks through Chimney-Type Electric Heating and Natural Circulation

Beithou Nabil, Abdallatif Nassir, Khalid Mohammad Bani, Alsaqoor Sameh, Alahmer Ali, Borowski Gabriel, As’ad Samer, Attar Hani, Andruszkiewicz Artur

Advances in Science and Technology. Research Journal

|

2024

|

Vol. 18, no 3

151--160

EN

Hot storage tanks (HST) are known for their high energy consumption, attributed to variations in usage, heat dissipation within the tank, and heat losses to the surroundings. This study proposes a chimney-type electrically heated HST, which is investigated under static mode to enhance its thermal performance. Different natural circulation areas (chimney areas) with large (9.5 cm diameter), medium (2.5 cm diameter), and small (1.5 cm diameter) sizes were utilized to examine the effect of natural circulation on the HST performance. Additionally, the influence of chimney insulation on the HST performance was also studied. The experiments revealed that the chimney significantly affected the thermal stratification within the tank. Different chimney contact diameters (9.5 cm, 2.5 cm, and 1.5 cm) were tested, showing varying degrees of thermal stratification. The results indicated that smaller chimney contact diameters led to higher thermal stratification and more rapid heating of the top layer temperatures. However, the impact of insulation on thermal performance was inconclusive, suggesting the need for more effective insulation and further investigation into the dynamic mode of operation. The findings also highlighted the faster heating of the top outer layer compared to the larger diameter, emphasizing the significance of the chimney type electrical heater in the hot storage tank.

2

Natural circulation in two-phase thermosyphon loop heated from below

Bieliński H., Mikielewicz J.

Archives of Thermodynamics

|

2004

|

Vol. 25, no. 3

15-26

EN

Closed thermosyphon loops are devices capable of transporting heat through natural convection process. This paper focuses on the steady-state behaviour of two-phase natural circulation loops i.e. thermosyphon loops, in which the density difference of fluid between its liquid and vapour phases is a driving force. The steady-state, one-dimensional model is proposed for two-phase thermosyphon. The presented model based on mass, momentum, and energy balances in the evaporator, rising tube, condenser, and the falling tube. The slip two-phase flow model is used in circulations. The effect of the loop.s aspect ratio (height H to the breadth B) on the mass flow rate at the steady-state is examined numerically. Results show that the mass flow rate increases with increasing aspect ratio H/B. Freon R-11 was chosen as a working fluid in the thermosyphon device.

3

Experimental study on flashing and flashing induced instabilities during the start-up of natural-circulation-cooled boiling water reactors

Manera A., Hagen T., Kruijf W.

Archives of Thermodynamics

|

2002

|

Vol. 23, no 3

105-118

EN

The characteristics of flashing-induced instabilities, which are of importance for the start up of natural-circulation boiling water reactors, are studied. Experiments at typical start-up conditions (low power and low pressure) are carried out on a steam/water natural circulation loop. Flashing and the mechanism of flashing-induced instability are analysed.

4

New solutions of thermal diode with natural laminar circulation

Bieliński H., Mikielewicz J.

Archives of Thermodynamics

|

2001

|

Vol. 22, nr 1-2

89-106

EN

The thermal diode allows the heat to be transferred in one direction, preventing the transfer of heat in the opposite direction. Two new models of the thermal diode are presented in this paper. The first model describes the thermal diode heated simultaneously from below and symmetrically from the sides, whilst the second model demonstrates the thermal diode heated from a lower part of one side and cooled from the upper part of the opposite side. The analysis of fluid flow and heat transfer is based on a one-demensional model. Distributions of temperature and mass flow rate are obtained for steady-state laminar flow. Numerical calculations are performed for the onset of motion of the fluid from rest. It is shown that the geometrical and thermal parameters have an influence on both the steady-state flow rate and the problem of global flow initiation from the rest.