title: A modified energy transfer diagram for heat exchanger network retrofit bridge analysis

authors: Walmsley, Michael R.W.

abstract: The aim of this paper is to modify the Energy Transfer Diagram (ETD) to be able to graphically determine retrofit options and the amount of heat transferred. The ETD is a graphical methodology to represent a process and/or Heat Exchanger Network (HEN). For HENs, the ETD contains valuable information about where in the network exist heat surpluses and deficits, after considering a global (or contribution) minimum approach temperature. The important advancement in this work is the identification of which segments of the ETD represent heat surplus/deficit within a heat exchanger and then to show this on the ETD. Further clarity is drawn from the labelling of what segments relate to which process stream. Behind the ETD is the well-known surplus/deficit cascade for each heater, cooler, and exchanger, which is also analysed and presented to reinforce the graphical approach. A simple four-stream problem with an existing HEN that falls 1,950 kW short of Pinch targets is used to demonstrate the methodological step forward. In the example, the initial network has a total of 5 heat exchangers and after two bridge modifications the Maximum Energy Recovery network is achieved, which requires 8 heat exchangers.

text: A modified energy transfer diagram for heat exchanger network retrofit bridge analysis The aim of this paper is to modify the Energy Transfer Diagram (ETD) to be able to graphically determine retrofit options and the amount of heat transferred. The ETD is a graphical methodology to represent a process and/or Heat Exchanger Network (HEN). For HENs, the ETD contains valuable information about where in the network exist heat surpluses and deficits, after considering a global (or contribution) minimum approach temperature. The important advancement in this work is the identification of which segments of the ETD represent heat surplus/deficit within a heat exchanger and then to show this on the ETD. Further clarity is drawn from the labelling of what segments relate to which process stream. Behind the ETD is the well-known surplus/deficit cascade for each heater, cooler, and exchanger, which is also analysed and presented to reinforce the graphical approach. A simple four-stream problem with an existing HEN that falls 1,950 kW short of Pinch targets is used to demonstrate the methodological step forward. In the example, the initial network has a total of 5 heat exchangers and after two bridge modifications the Maximum Energy Recovery network is achieved, which requires 8 heat exchangers.

year: 2017

title: Constructing English in New Zealand: A report on a decade of reform

authors: Locke, Terry

subjects: English

abstract: In 1991, the newly elected National Government of New Zealand set in train a major reform of the New Zealand national curriculum and, a little later, a major reform of the New Zealand qualifications system. These reforms have had a major impact on the construction of English as a subject in New Zealand secondary schools, and the work and professional identity of teachers. This article uses as a basis for analysis a framework which posits four paradigms for subject English and proceeds to examine the current national English curriculum in New Zealand for its underlying discourses. In specific terms, it explores questions of partition and progression, and terminology. In respect of progression, it argues that the current curriculum has imposed a flawed model on teachers and students, in part because of its commitment to the assignment of decontextualised outcomes statements (‘achievement objects’) to staged levels of student development (levels). It also argues that much of the terminology used by the document has had a negative impact on metalinguistic classroom practice. Finally, while it views the national English curriculum as a discursively mixed bag, it notes an absence of critical discourses and a tendency, in recent qualifications reforms, to construct English teachers as technicians and the subject as skills-based.

text: Constructing English in New Zealand: A report on a decade of reform In 1991, the newly elected National Government of New Zealand set in train a major reform of the New Zealand national curriculum and, a little later, a major reform of the New Zealand qualifications system. These reforms have had a major impact on the construction of English as a subject in New Zealand secondary schools, and the work and professional identity of teachers. This article uses as a basis for analysis a framework which posits four paradigms for subject English and proceeds to examine the current national English curriculum in New Zealand for its underlying discourses. In specific terms, it explores questions of partition and progression, and terminology. In respect of progression, it argues that the current curriculum has imposed a flawed model on teachers and students, in part because of its commitment to the assignment of decontextualised outcomes statements (‘achievement objects’) to staged levels of student development (levels). It also argues that much of the terminology used by the document has had a negative impact on metalinguistic classroom practice. Finally, while it views the national English curriculum as a discursively mixed bag, it notes an absence of critical discourses and a tendency, in recent qualifications reforms, to construct English teachers as technicians and the subject as skills-based.

year: 2007

title: Monitoring and hydrodynamic modelling of groundwater inflows into Lake Rotokakahi, New Zealand

authors: Noakes, Katie

subjects: Groundwater

abstract: Lake Rotokakahi is located 10 km south of Rotorua and is of immense cultural importance to the local iwi. The lake also has significant historical and recreational values, which prompted iwi to make the lake private in 1996. Lake Rotokakahi is one of several Rotorua/ Te Arawa lakes. Several of these lakes have become eutrophic and some have declining water quality. This study was prompted by declining water quality of Lake Rotokakahi and the need to identify potential sources of nutrients to the lake, particularly groundwater inflows.

The interaction between groundwater and surface water has a major influence on the trophic status of lakes, particularly those that are predominantly or solely groundwater fed systems. Lake Rotokakahi has one small spring-fed surface water inflow and one outflow, the Te Wairoa stream. Thus the lake is predominantly groundwater fed. The main objective of this thesis was to quantify the contribution of groundwater and surface water to Lake Rotokakahi and to examine interactions of the groundwater system with the lake, in order to provide a basis to improve lake management practices. Multiple monitoring sites were established around the perimeter of the lake to determine the spatial and temporal variation of groundwater inputs, as well as the groundwater nutrient dynamics. A three-dimensional hydrodynamic lake model was set up and simulations were used to examine how groundwater and surface water inflows were dispersed within the lake upon entry.

Monitoring of the shallow groundwater system took place from 1 January to 1 July 2016. Three separate storm events were monitored at high frequency within this monitoring period. The monitoring results showed the groundwater system varied significantly both spatially and temporally and also contributed a high proportion of the total nutrient load to the lake. Groundwater discharge and nutrient concentrations generally increased in association with or immediately following high rainfall events.
 
The three-dimensional model ELCOM was set up using hydrological data for the catchment, meteorological data from a nearby station and bathymetry of the lake. Simulations were based upon different methods of calculating groundwater inflows. Simulation 1 was based upon the common water balance equation method. Simulation 2 used constant groundwater inflow and outflow volumes as determined by a groundwater flow model, MODFLOW, which had been applied to the catchment by White et al., (2015). Simulation 3 combined MODLFOW values and measured groundwater levels to create a varying inflow volume based on water level. The three simulations accurately captured surface and bottom temperatures and had varying lake water levels. Only simulation 3 accurately captured the presence of the groundwater spring near the lake shore and was concluded the more accurate method of groundwater inflow calculation.

text: Monitoring and hydrodynamic modelling of groundwater inflows into Lake Rotokakahi, New Zealand Lake Rotokakahi is located 10 km south of Rotorua and is of immense cultural importance to the local iwi. The lake also has significant historical and recreational values, which prompted iwi to make the lake private in 1996. Lake Rotokakahi is one of several Rotorua/ Te Arawa lakes. Several of these lakes have become eutrophic and some have declining water quality. This study was prompted by declining water quality of Lake Rotokakahi and the need to identify potential sources of nutrients to the lake, particularly groundwater inflows.

The interaction between groundwater and surface water has a major influence on the trophic status of lakes, particularly those that are predominantly or solely groundwater fed systems. Lake Rotokakahi has one small spring-fed surface water inflow and one outflow, the Te Wairoa stream. Thus the lake is predominantly groundwater fed. The main objective of this thesis was to quantify the contribution of groundwater and surface water to Lake Rotokakahi and to examine interactions of the groundwater system with the lake, in order to provide a basis to improve lake management practices. Multiple monitoring sites were established around the perimeter of the lake to determine the spatial and temporal variation of groundwater inputs, as well as the groundwater nutrient dynamics. A three-dimensional hydrodynamic lake model was set up and simulations were used to examine how groundwater and surface water inflows were dispersed within the lake upon entry.

Monitoring of the shallow groundwater system took place from 1 January to 1 July 2016. Three separate storm events were monitored at high frequency within this monitoring period. The monitoring results showed the groundwater system varied significantly both spatially and temporally and also contributed a high proportion of the total nutrient load to the lake. Groundwater discharge and nutrient concentrations generally increased in association with or immediately following high rainfall events.
 
The three-dimensional model ELCOM was set up using hydrological data for the catchment, meteorological data from a nearby station and bathymetry of the lake. Simulations were based upon different methods of calculating groundwater inflows. Simulation 1 was based upon the common water balance equation method. Simulation 2 used constant groundwater inflow and outflow volumes as determined by a groundwater flow model, MODFLOW, which had been applied to the catchment by White et al., (2015). Simulation 3 combined MODLFOW values and measured groundwater levels to create a varying inflow volume based on water level. The three simulations accurately captured surface and bottom temperatures and had varying lake water levels. Only simulation 3 accurately captured the presence of the groundwater spring near the lake shore and was concluded the more accurate method of groundwater inflow calculation.

year: 2016