04 Fakultät Energie-, Verfahrens- und Biotechnik

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/5

Browse

Filters

1991 - 199912010 - 20111

Settings

Institute: search.filters.UBSInstitut.Institut für Thermodynamik und WärmetechnikSubject: search.filters.subject.530

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Effektive Wärmeleitfähigkeit des Mitteltemperatur-Metallhydrids LaNi4,7Al0,3Hx in Pulverform
    (1991) Kallweit, Jörg; Groß, Ulrich; Hahne, Erich
    Die Kenntnis der effektiven Wärmeleitfähigkeit wird - neben anderen thermophysikalischen Stoffeigenschaften- zur praktischen Auslegung von Metallhydrid-Speichern benötigt. Insbesondere stellt sie eine entscheidende Stoffeigenschaft für die Vorausberechnung der Be- und Entladezeiten eines Speichers dar. In der vorliegenden Arbeit werden Versuchsergebnisse für eine Pulverschüttung des Mitteltemperatur-Metallhydrids LaNi4,7Al0,3Hx vorgestellt.
  • Thumbnail Image
    ItemOpen Access
    Investigation of the effects of baffle orientation, baffle cut and fluid viscosity on shell side pressure drop and heat transfer coefficient in an e-type shell and tube heat exchanger
    (2011) Mohammadi, Koorosh; Müller-Steinhagen, Hans (Prof. Dr. Dr.-Ing. habil.)
    The commercial CFD code FLUENT is used to determine the effect of baffle orientation and baffle cut as well as viscosity of the working fluid on the shell-side heat transfer and pressure drop of a shell and tube heat exchanger. The shell and tube heat exchangers considered follow the TEMA standards. The investigation has been completed in three stages: 1. The shell and tube heat exchanger consists of 660 plain tubes with fixed outside diameter which are arranged in a triangular layout. Horizontal and vertical baffle orientations as well as three baffle cuts, 20%, 24% and 30% of shell inside diameter, are considered. No leakage flow in tube-to-baffle gaps and baffle-to-shell gaps is considered. The investigation has been applied for the inlet zone, in order to find the effect of baffle orientation, baffle cut and viscosity of shell-side fluid on the shell-side performance of the inlet zone. For each baffle orientation, baffle cut and working fluid, different flow velocities at inlet are investigated. These velocities are introduced as inlet Reynolds number. Heat transfer and pressure drop are reported as overall Nusselt number and Kârmân number, respectively. A shell-side gain factor suitable for the assessment of shell and tube heat exchangers is introduced as ratio of the shell-side heat transfer coefficient to the shell-side pressure drop. To facilitate the decision between horizontal and vertical baffle orientation, a performance factor is used as ratio of the gain factor for horizontally orientated baffles to the gain factor for vertical baffle orientation. The simulation results show the advantage of the horizontal baffle orientation over the vertical orientation, especially for air as shell-side fluid. At baffle cut 30%, the performance factor reaches its maximum value for all shell-side fluids, while the minimum value of performance factor is observed at baffle cut 24%. 2. In order to simulate the complete shell and tube heat exchanger, a shell and tube heat exchanger with the same geometrical aspects used in the previous stage is considered. Again, no leakage flows are taken into account. For the numerical investigations the heat exchanger is subdivided into eight different flow sections such as the inlet zone, six intermediate flow sections located between adjacent baffles and the outlet zone. Simulations are performed for the two working fluids; air and water. For each baffle orientation, baffle cut and working fluid, simulations are performed for five inlet Reynolds numbers. The simulation results show the advantage of the horizontal baffle orientation over the vertical orientation, particularly in the inlet and outlet zone for all investigated shell-side fluids. The performance factor for horizontal baffle orientation is approximately equal to the performance factor for vertical baffle orientation at intermediate baffle spacing zones when liquid water is used as shell-side fluid. For air, the benefit of vertical baffle orientation on horizontal baffle orientation is noticeable. 3. In order to simulate a real complete heat exchanger, a shell and tube heat exchanger consisting of 76 tubes with fixed outside diameter is considered. The tubes are arranged in a triangular layout. The tube-to-baffle and baffle-to-shell leakages are also taken into account. Similar to the previous stages, horizontal and vertical baffle orientations are considered, but the baffle cut is fixed to 20% of shell inside diameter. Simulations are performed for three working fluids air, water and engine oil. For each baffle orientation, baffle cut and working fluid, simulations are performed for five inlet Reynolds numbers. The simulation results show the advantage of the horizontal baffle orientation over the vertical orientation, particularly in the inlet and outlet zone for all investigated shell-side fluids. The simulation results show a significant influence of the baffle orientation on the shell-side pressure drop and heat transfer of shell and tube heat exchangers. The results show that in shell and tube heat exchanger with leakage flows the vertical baffle orientation seems to be more advantageous than the horizontal orientation. The benefit of vertical baffle orientation over horizontal baffle orientation is more noticeable for gases.