Assessing site performance of large mine water chilling machines using refrigerant-circuit measurements and machine modelling
A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, Johat.nesburq, in fulfilment of the requirements for the degree of Doctor of Philosophy Johannesburg, 1998 === This thesis contributes to accurate, practicable techniques of ascertaining and assessing site perform...
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ndltd-netd.ac.za-oai-union.ndltd.org-wits-oai-wiredspace.wits.ac.za-10539-204412019-05-11T03:39:47Z Assessing site performance of large mine water chilling machines using refrigerant-circuit measurements and machine modelling Bailey-McEwan, Michael Refrigerants Mining engineering Refrigeration and refrigerating machinery A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, Johat.nesburq, in fulfilment of the requirements for the degree of Doctor of Philosophy Johannesburg, 1998 This thesis contributes to accurate, practicable techniques of ascertaining and assessing site performance of large refrigerating machines chilling water 'for cooling deep South African mines. It applies to all vapourcompression machines cooling fluids in steady, continuous processes. To assess whether a water chilling machine is performing satisfactorily, both its actual performance, and the corresponding normal or optimal performance of which it is capable, must be ascertained. Both requirements r esent difficulties on site. in particular, the traditional "heat balance" method of verifying the apparent performance obtained from measurements in the water circuits does not prove that such performance is accurate. The calibration of typical site instrumentation is not assured, so an "acceptable" heat imbalance may conceal large but similar errors - which thus also balance out - in the apparent constituents of the heat balance. Three methods of independently ascertaining actual performance, so verifying apparent performance, are presented, The first is an enhanced method, applicable to custom-built machines as well as conventional ones, of ascertaining the efficiency of the actual refrigerating process from measurements in the refrigerant circuit. This detects errors concealed in an "acceptable" heat balance. Where some refrigerant-circuit measurements are unavailable, an inexact version of this method still indicates the relative likelihood of the apparent performance being acceptably accurate. The third method, where these two are inadequate, is ascertaining actual performance using available measurements and fundamental machine modelling. Such modelling is also the most versatile method of predicting corresponding normal or optimal performance. A computer program simulating complete mine water chilling installations is used here. Actual performance can then be meaningfully assessed and appropriate remedial action justified, as shown in seven case studies. An outcorr.e for conventional water chillinq machines with a centrifugal compressor is that keeping heat exchangers clean may prejudice efficiency under part-duties lf a machine has been designed for optimum efficiency at full duty. An alternative control philosophy of maximising the machine load may then yield better performance. If these techniques are included ill an automated system of fault diagnosis, they will be of most use to burdened mine staff, who are generally not refrigeration experts. 2016-06-08T07:49:09Z 2016-06-08T07:49:09Z 2016-06-08 Thesis http://hdl.handle.net/10539/20441 en application/pdf application/pdf |
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Refrigerants Mining engineering Refrigeration and refrigerating machinery |
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Refrigerants Mining engineering Refrigeration and refrigerating machinery Bailey-McEwan, Michael Assessing site performance of large mine water chilling machines using refrigerant-circuit measurements and machine modelling |
description |
A thesis submitted to the Faculty of Engineering, University of the
Witwatersrand, Johat.nesburq, in fulfilment of the requirements for the
degree of Doctor of Philosophy
Johannesburg, 1998 === This thesis contributes to accurate, practicable techniques of ascertaining
and assessing site performance of large refrigerating machines chilling
water 'for cooling deep South African mines. It applies to all vapourcompression
machines cooling fluids in steady, continuous processes.
To assess whether a water chilling machine is performing satisfactorily,
both its actual performance, and the corresponding normal or optimal
performance of which it is capable, must be ascertained. Both
requirements r esent difficulties on site. in particular, the traditional "heat
balance" method of verifying the apparent performance obtained from
measurements in the water circuits does not prove that such performance
is accurate. The calibration of typical site instrumentation is not assured,
so an "acceptable" heat imbalance may conceal large but similar errors -
which thus also balance out - in the apparent constituents of the heat
balance.
Three methods of independently ascertaining actual performance, so
verifying apparent performance, are presented, The first is an enhanced
method, applicable to custom-built machines as well as conventional
ones, of ascertaining the efficiency of the actual refrigerating process from
measurements in the refrigerant circuit. This detects errors concealed in
an "acceptable" heat balance. Where some refrigerant-circuit
measurements are unavailable, an inexact version of this method still
indicates the relative likelihood of the apparent performance being
acceptably accurate. The third method, where these two are inadequate,
is ascertaining actual performance using available measurements and
fundamental machine modelling.
Such modelling is also the most versatile method of predicting
corresponding normal or optimal performance. A computer program
simulating complete mine water chilling installations is used here. Actual
performance can then be meaningfully assessed and appropriate
remedial action justified, as shown in seven case studies. An outcorr.e for
conventional water chillinq machines with a centrifugal compressor is that
keeping heat exchangers clean may prejudice efficiency under part-duties
lf a machine has been designed for optimum efficiency at full duty. An
alternative control philosophy of maximising the machine load may then
yield better performance.
If these techniques are included ill an automated system of fault
diagnosis, they will be of most use to burdened mine staff, who are
generally not refrigeration experts. |
author |
Bailey-McEwan, Michael |
author_facet |
Bailey-McEwan, Michael |
author_sort |
Bailey-McEwan, Michael |
title |
Assessing site performance of large mine water chilling machines using refrigerant-circuit measurements and machine modelling |
title_short |
Assessing site performance of large mine water chilling machines using refrigerant-circuit measurements and machine modelling |
title_full |
Assessing site performance of large mine water chilling machines using refrigerant-circuit measurements and machine modelling |
title_fullStr |
Assessing site performance of large mine water chilling machines using refrigerant-circuit measurements and machine modelling |
title_full_unstemmed |
Assessing site performance of large mine water chilling machines using refrigerant-circuit measurements and machine modelling |
title_sort |
assessing site performance of large mine water chilling machines using refrigerant-circuit measurements and machine modelling |
publishDate |
2016 |
url |
http://hdl.handle.net/10539/20441 |
work_keys_str_mv |
AT baileymcewanmichael assessingsiteperformanceoflargeminewaterchillingmachinesusingrefrigerantcircuitmeasurementsandmachinemodelling |
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1719080703211077632 |