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Heat and Mass Transfer

, Volume 55, Issue 1, pp 67–79 | Cite as

Influence of different heating types on the pumping performance of a bubble pump

  • Bernd BierlingEmail author
  • Fabian Schmid
  • Klaus Spindler
Original

Abstract

This study presents an experimental investigation of the influence of different heating types on the pumping performance of a bubble pump. A test rig was set up at the Institute of Thermodynamics and Thermal Engineering (ITW), University of Stuttgart. The vertical lift tube is made of copper with an inner diameter of 8 mm and a length of 1.91 m. The working fluid is demineralized water. The test rig offers the possibility to vary the supplied heat flow (0 W − 750 W), the resulting supplied heat flux and the location of the heating. Investigations were carried out using spot heating, partial-length heating and full-length heating. A Coriolis mass flowmeter was successfully implemented which measures the vapor mass flow rate continuously. The improvement of the vapor mass flow rate measurement by using the continuous measurement method compared to a discontinuous one is discussed. Furthermore, the influence of an unstable inlet temperature of the working fluid entering the lift tube on the pumping performance is investigated. The focus of this publication lies on the build-up of the test rig with the measurement setup and the analysis of the pumping performance for the three heating types. The measurement results show a big influence of the heating type on the pumping performance. The lower the relative length of the heating, the higher is the pumping ratio which is defined as the lifted liquid mass flow rate in relation to the generated vapor mass flow rate.

Abbreviations

A

Amperemeter

d

Downwards

DAR

Diffusion absorption refrigerator

u

Upwards

V

Voltmeter

Latin symbols

A

Cross sectional area (m2)

b

Pumping ratio (−)

cp

Specific heat capacity at constant pressure (kJ kg−1 K−1)

D

Diameter (m)

g

Gravitational acceleration (m s−2)

ΔH

Height (m)

Δhv

Specific enthalpy of evaporation (kJ kg−1)

L

Length (m)

\( \dot{M} \)

Mass flow rate (kg s−1)

P

Power (W)

Δp

Relative pressure (bar)

\( \dot{Q} \)

Heat flow (W)

\( \dot{q} \)

Heat flux (W m−2)

S

Slip ratio (−)

SR

Submergence ratio (−)

t

Time (min)

\( \dot{V} \)

Volumetric flow rate (m3 h−1)

w

Velocity (m s−1)

x

Coordinate in flow direction (m)

Greek symbols

ϑ

Celsius temperature (°C)

ϑs

Boiling temperature (°C)

λ

Thermal conductivity (W m−1 K−1)

ρ

Density (kg m−3)

\( \overline{\rho} \)

Mean density over length (kg m−3)

φ

Relative length of heating (−)

Subscripts

amb

Ambient

cartr

Cartridges

disc

Discontinuous

el

Electric

evap

Evaporation

ext

External

f

Friction

FDR

Friction dominant regime

GDR

Gravity dominant regime

heat

Supplied heat flow

HX2

Double-pipe heat exchanger 2

in

At the inlet

L

Liquid

LT

Lift tube

m

Mean

mass

Related to the mass

max

Maximum

min

Minimum

out

At the outlet

part

Partial

preheat

Preheating

rel

Relative

res

Reservoir

TP

Two-phase

V

Vapor

vol

Related to the volume

Notes

Acknowledgements

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Compliance with ethical standards

Conflict of interest

On behalf of all authors, the corresponding author states that there is no conflict of interest.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2017

Authors and Affiliations

  1. 1.Institute of Thermodynamics and Thermal Engineering (ITW)University of StuttgartStuttgartGermany

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