title: Flexibility Analysis of Heat Exchanger Network Retrofit Designs using Monte Carlo Simulation

authors: Lal, Nathan S.

abstract: The aim of this paper is to use Monte Carlo Simulation (MCS) to conduct an analysis of the flexibility and controllability of retrofitted Heat Exchanger Network (HEN) designs. Historical plant data is often uncertain and variable but is an important tool for understanding the real-time operation of a HEN. MCS uses these uncertainties to give an analysis of the retrofitted HENs, and it can be used in a more detailed analysis of the controllability and flexibility. Using Monte Carlo Simulation, inflexibility has been defined as the probability of a HEN to fail to meet temperature targets within defined tolerances. Inflexibility can be used as a tool to guide the retrofit analysis of a HEN. A retrofit HEN design should improve the flexibility of the network without compromising on the expected energy savings. The proposed method is demonstrated using a four-stream HEN problem. The inflexibility of the network was shown to be improved with bypass control and optimal allocation of retrofit area and the proposed method succeeds in augmenting the retrofit design method so that cost-effective, flexible retrofit HENs can be identified.

text: Flexibility Analysis of Heat Exchanger Network Retrofit Designs using Monte Carlo Simulation The aim of this paper is to use Monte Carlo Simulation (MCS) to conduct an analysis of the flexibility and controllability of retrofitted Heat Exchanger Network (HEN) designs. Historical plant data is often uncertain and variable but is an important tool for understanding the real-time operation of a HEN. MCS uses these uncertainties to give an analysis of the retrofitted HENs, and it can be used in a more detailed analysis of the controllability and flexibility. Using Monte Carlo Simulation, inflexibility has been defined as the probability of a HEN to fail to meet temperature targets within defined tolerances. Inflexibility can be used as a tool to guide the retrofit analysis of a HEN. A retrofit HEN design should improve the flexibility of the network without compromising on the expected energy savings. The proposed method is demonstrated using a four-stream HEN problem. The inflexibility of the network was shown to be improved with bypass control and optimal allocation of retrofit area and the proposed method succeeds in augmenting the retrofit design method so that cost-effective, flexible retrofit HENs can be identified.

year: 2019

title: Test of AMS 14C dating of pollen concentrates using tephrochronology

authors: Newnham, Rewi M.

subjects: AMS radiocarbon dating

abstract: Previous attempts to radiocarbon date sediments >10 kyr from the high rainfall region of Westland, New Zealand, a critical location for investigation of interhemispheric patterns of climate change, have been problematic. This study, building on recent work by Vandergoes and Prior (2003), shows that AMS 14C dating of pollen concentrates has potential to provide more reliable ages than other sediment constituents, including plant macrofossils. The method was applied to sediments from three sites containing the 22.6k 14C yr Kawakawa Tephra, which provided an independent test of the 14C ages. Although some minor laboratory contamination was detected in tests on background standards, the modelled relationship between sample mass and measured 14C content permitted an appropriate correction to be determined. Improved pollen concentrations derived by density separation between 1.4 and 1.2 specific gravity and sieving in the range 10-50  m provided either older ages than other fractions of the same sample or, where in situ contamination was not evident, equivalent ages. Differences in degree of in situ contamination between depositional environments indicated that, in Westland, lake sites may be less susceptible to contamination by younger carbon than peat sites, where this process may be facilitated by root penetration into underlying sediments.

text: Test of AMS 14C dating of pollen concentrates using tephrochronology Previous attempts to radiocarbon date sediments >10 kyr from the high rainfall region of Westland, New Zealand, a critical location for investigation of interhemispheric patterns of climate change, have been problematic. This study, building on recent work by Vandergoes and Prior (2003), shows that AMS 14C dating of pollen concentrates has potential to provide more reliable ages than other sediment constituents, including plant macrofossils. The method was applied to sediments from three sites containing the 22.6k 14C yr Kawakawa Tephra, which provided an independent test of the 14C ages. Although some minor laboratory contamination was detected in tests on background standards, the modelled relationship between sample mass and measured 14C content permitted an appropriate correction to be determined. Improved pollen concentrations derived by density separation between 1.4 and 1.2 specific gravity and sieving in the range 10-50  m provided either older ages than other fractions of the same sample or, where in situ contamination was not evident, equivalent ages. Differences in degree of in situ contamination between depositional environments indicated that, in Westland, lake sites may be less susceptible to contamination by younger carbon than peat sites, where this process may be facilitated by root penetration into underlying sediments.

year: 2007-01

title: Maori perspectives of the environment: A review of Environment Waikato information sources.

authors: Whangapirita, Laura

subjects: Maori

abstract: The Community and Economy Programme at Environment Waikato has developed a partnership with the Maori and Psychology Research Unit of the University of Waikato to further assist in strengthening its commitment to cultural research and information work. This relationship will facilitate the development of a number of significant research reports throughout 2003.  This initial report describes an internal review conducted by the Maori and Psychology Research Unit to identify what information Environment Waikato currently holds on Maori environmental perspectives.

text: Maori perspectives of the environment: A review of Environment Waikato information sources. The Community and Economy Programme at Environment Waikato has developed a partnership with the Maori and Psychology Research Unit of the University of Waikato to further assist in strengthening its commitment to cultural research and information work. This relationship will facilitate the development of a number of significant research reports throughout 2003.  This initial report describes an internal review conducted by the Maori and Psychology Research Unit to identify what information Environment Waikato currently holds on Maori environmental perspectives.

year: 2003-05