TNO Institute of Environmental and Energy Technology

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1 TNO Institute of Environmental and Energy Technology Laan van Westenenk 51 P.O. Box AH Apeldoorn The Netherlands Telex tnoap nl Phone Fax TNO-report Removal of suspended solids by the Flamcovent Clean Reference number R95-64 File number Date February 1995 NP Authors Ir. J.W. Assink W.G. van Marwijk Key words - water circuits - particles - separation All rights reserved. No part of this publication may be reproduced and / or published by print, photoprint, microfilm or any other means without previous written consent of TNO. Intended for Flamco B.V. P.O. box AC Gouda The Netherlands In case this report was drafted on instructions, the rights and obligations of contracting parties are subject to either the Standard Conditions for Research Instructions given to TNO, or the relevant agreement concluded between the contracting parties. Submitting the report for inspection to parties who have a direct interest is permitted. TNO Based on the necessity for a sustainable development of society, the TNO Institute of Environmental and Energy Research aims at contributing, through research and advise, to adequate environmental management, rational energy consumption and the proper management and use of subsurface natural resources. Netherlands organization for applied scientific research. The Standard Conditions for Research Instructions given to TNO, as filed at the Registry of the District Court and the Chamber of Commerce in The Hague shall apply to all instructions given to TNO

2 Table of contents 1 Introduction Experiments and results...4 3Conclusions Authentication...1 R95-64/

3 1 Introduction The Flamcovent is a micro bubble air separator for heating and cooling installations, produced by Flamco BV in the Netherlands. Practical experience and previous research revealed the ability of the Flamcovent to remove suspended solids from the water circuit as well. The removal of these particles from the water circuit is attractive, because they could contribute to the erosion and obstruction of the pump. The new Flamcovent Clean has been specially developed to optimize the solids removing feature of the micro-bubble separator. The Dutch Organisation of Applied Scientific Research (TNO) has assessed the solids removal efficiency of the new Flamcovent Clean at the commission of Flamco B.V. This report is a summary of the full TNO-report (reference number , december 1994). R95-64/

4 2 Experiments and results The solids removal efficiency of the Flamcovent has been assessed in a small circulation system (5 liters) using sand particles as a model for the suspended solids. The sand sample is composed of 5 fractions between 38 µm and 25 µm and has a density of sand of 265 kg/m 3. Experiments have been carried out with a Flamcovent Clean, specially equipped with a removable bottom plate in order to facilitate the rinsing of the interior. The flow rate in the circuit was either.5 m/s (3.5 m 3 /h) or 1. m/s (7.1 m 3 /h). The amount of particles in the Flamcovent and the remaining amount in the water circuit were determined after a circulation fold of 2 or 5 (i.e. the water volume of the circuit has passed the Flamcovent 2 or 5 times). The solids removal efficiency is calculated by the following formula: Mass in Flamcovent Mass in Flamcovent + Mass in circuit The removal efficiences are determined for the total sand sample, as well as the fractions µm, µm, µm, µm and µm. The results of four experiments are presented in table 1 to 4 and the figures 1 to 4. Table 5 summarizes the results of the experiments 3 to 6. Figure 5 presents the overall removal efficiency of the Flamcovent Clean, as a function of the circulation fold and the flow speed. The curves in the figure are based on the assumption of logarithmic relation between the circulation fold and the solids removal. Table 1 Experiment 3 with Flamcovent Clean; Circulation fold = 2; v = 1 m/s Particle size Recovery from Remaining in Total Removal Flamcovent circuit efficiency (µm) (g) (g) (g) (%) Cumulative R95-64/

5 Table 2 Experiment 4 with Flamcovent Clean; Circulation fold = 2; v =,5 m/s Particle size Recovery from Remaining in Total Removal Flamcovent circuit efficiency (µm) (g) (g) (g) (%) Cumulative Table 3 Experiment 5 with Flamcovent Clean; Circulation fold = 5; v =,5 m/s Particle size Recovery from Remaining in Total Removal Flamcovent circuit efficiency (µm) (g) (g) (g) (%) Cumulative Table 4 Experiment 6 with Flamcovent Clean; Circulation fold = 5; v = 1 m/s Particle size Recovery from Remaining in Total Removal Flamcovent circuit efficiency (µm) (g) (g) (g) (%) Cumulative R95-64/

6 Flamcovent Clean 8 8 Weight (g) Removal (%) Particle-size (µm) Flamcovent Total system Removal efficiency (right y-axis) Figure 1 Removal of suspended particles, experiment 3; v = 1, m/s and circulation fold = 2 Flamcovent Clean 8 8 Weight (g) Removal (%) Particle-size (µm) Flamcovent Total system Removal efficiency (right y-axis) Figure 2 Removal of suspended particles, experiment 4; v =,5 m/s and circulation fold = 2 R95-64/

7 Flamcovent Clean 8 8 Weight (g) Removal (%) Particle-size (µm) Flamcovent Total system Removal efficiency (right y-axis) Figure 3 Removal of suspended particles, experiment 5; v =,5 m/s and circulation fold = 5 Flamcovent Clean 8 8 Weight (g) Removal (%) Particle-size (µm) Flamcovent Total system Removal efficiency (right y-axis) Figure 4 Removal of suspended particles, experiment 6; v = 1, m/s and circulation fold = 5 R95-64/

8 Table 5 Summary of results Experiment Flow rate Circulation Removal efficiency (%) number (m/s) fold Overall Fine Coarse fraction (38-25 µm) (38-63 µm) ( µm) Overall removal efficiency (%) Flow =,5 m/s 1 Flow = 1, m/s Circulation fold Figure 5 The overall removal efficiency (38 25 µm particles) of the Flamcovent Clean for two different flow rates R95-64/

9 3 Conclusions The Flamcovent Clean has a better performance in separating suspended particles than the conventional Flamcovent (compare TNO-report ). This holds for both fine and coarse particles. The removal efficiency of suspended particles increases with: - decreasing flow velocity ; - increasing circulation fold; - increasing settling velocity of particles, hence with larger and more dense particles. Flamcovent Clean proves to be well capable of removing suspended particles from a water circuit. Sand particles larger than 38 µm (or particles with a similar sedimentation behaviour) are removed to well over 99% at the circulation fold of 5, using a flow rate of.5 m/s. Although lower removal efficiencies are obtained at a flow rate of 1. m/s, still over 9% of the fine particles (38-63 µm) and over 99% of the course fraction ( µm) is removed at a circulation fold of 5. R95-64/

10 4 Authentication Name and address of the principal Flamco B.V. P.O. Box AC Gouda The Netherlands Names and functions of the cooperators J.W Assink (research coordinator) W.G. van Marwijk (research employee) Names of establishments to which part of the research was put out to contract Date upon which, or period in which, the research took place September November 1994 ir. J.W. Assink research coordinator ir. C.L. van Deelen head of department of Environmental Technology R95-64/