title: Area targeting and storage temperature selection for heat recovery loops

authors: Walmsley, Michael R.W.

subjects: Actual temperature

abstract: Inter-plant heat integration across a large site can be achieved using a Heat Recovery Loop (HRL). In this paper the relationship between HRL storage temperatures, heating and cooling utility savings (heat recovery) and total HRL exchanger area is investigated. A methodology for designing a HRL based on a ΔTmin approach is compared to three global optimisation approaches where heat exchangers are constrained to have either the same Number of Heat Transfer Units (NTU), Log-Mean Temperature Difference (LMTD) or no constraints (actual global optimum). Analysis is performed using time averaged flow rate and temperature data. Attention is given to understanding the actual temperature driving force of the HRL heat exchangers compared to the apparent driving force as indicated by the composite curves. The cold storage temperature is also varied to minimise the total heat exchanger area. Results for the same heat recovery level show that the ΔTmin approach is effective at minimising total area to within 5 % of the unconstrained global optimisation approach. The study also demonstrates the efficiency of the ΔT min approach to HRL design compared to the other methods which require considerable computational resources.

text: Area targeting and storage temperature selection for heat recovery loops Inter-plant heat integration across a large site can be achieved using a Heat Recovery Loop (HRL). In this paper the relationship between HRL storage temperatures, heating and cooling utility savings (heat recovery) and total HRL exchanger area is investigated. A methodology for designing a HRL based on a ΔTmin approach is compared to three global optimisation approaches where heat exchangers are constrained to have either the same Number of Heat Transfer Units (NTU), Log-Mean Temperature Difference (LMTD) or no constraints (actual global optimum). Analysis is performed using time averaged flow rate and temperature data. Attention is given to understanding the actual temperature driving force of the HRL heat exchangers compared to the apparent driving force as indicated by the composite curves. The cold storage temperature is also varied to minimise the total heat exchanger area. Results for the same heat recovery level show that the ΔTmin approach is effective at minimising total area to within 5 % of the unconstrained global optimisation approach. The study also demonstrates the efficiency of the ΔT min approach to HRL design compared to the other methods which require considerable computational resources.

year: 2012

title: Microstructural controls on the geomechanics of coarse grained soft rocks; Waitemata Group, Auckland

authors: de la Mare, Graham Norman

abstract: The geomechanical behaviour of a variety of soft rocks from the Waitemata Group, Auckland, is characterised, and the influence of microstructure in determining the geomechanics examined. Field geotechnical measurements of joint spacing and Schmidt Hammer rebound are related to geomechanical properties to determine controls on joint development and applicability of field index tests for soft materials. Samples studied are dominantly sandstones, with one conglomerate; all of which have a significant component of swelling clay minerals. Low bulk densities, high porosities and large void ratios are characteristic of the samples.

They vary from extremely weak, very low durability rocks to moderately: strong and durable materials. Extremely weak sandstones are highly deformable and undergo plastic deformation when loaded in compression. The stronger samples undergo strain softening and respond elastically to applied stresses prior to brittle failure. High softening factors indicate that compressive and tensile strengths are greatly reduced upon saturation.

All the study rocks have high proportions of sand and silt size material (≤ 95 %), and up to 10 % of < 2 μ m proportions; significant gravel size material only occurs in the conglomerate. Volcanic and detrital rock fragments are the dominant constituents in all samples, with abundant quartz, minor calcic plagioclase, and a variety of accessory minerals. The dominant clay is smectite with lesser amounts of illite, kaolinite, and mixed-layer clays.

Individual sand and silt grains are dominantly subrounded to subangular quartz, regular bricks of feldspar, and rods of rutile, and are often clay coated. Microaggregates and grains are combined into aggregates and assemblages, and in some cases macroassemblages, to form granular arrangements, which produce a network of interconnecting pores. The fabric of the rocks is characterised by discontinuous matrices. Fabric types range from skeletal to turbostratic, and arrangements range from tightly interlocking grains to loose granular structures. Clay micro aggregates are either flocculated or form welded FF honeycomb arrangements.

Strength and durability are not influenced by quantity, size, or type of clasts or minerals present; rather, it is the arrangement of individual components (and associated pore spaces) in the rock fabric which directly determines the geomechanical behaviour. Strong, durable samples have an abundance of clean grain to grain contacts, and few large clay aggregates. Clay microaggregates are arranged in welded FF arrangements, and pore space is restricted to micropores which resist water infiltration. Progressively weaker rocks are characterised by an increase in clay coated grains, clay aggregates, and clay connectors (which form weak links for stress transmission), and interconnecting pores at all levels in the fabric. In the weakest rock macroassemblages of clay coated grains, and open flocculated smectitic aggregates connected by point contacts, produce a network of macropores, allowing easy access of water which flocculates clays into weaker states by reducing bonding and cohesion.

Schmidt rebound values in the field do not provide a useful indication of either compressive or tensile strength of these rocks. The rebound values do, however, correlate well with laboratory determined dynamic elasticity values, suggesting that the instrument should be used in the field to predict rock elasticity and not strength.

Joint spacing within the rock units is related to elasticity with units capable of storing stress through plastic deformation having reasonably wide, uniformly spaced joints. Units which release stress through brittle fracture have closely spaced, and more complex joint systems.

text: Microstructural controls on the geomechanics of coarse grained soft rocks; Waitemata Group, Auckland The geomechanical behaviour of a variety of soft rocks from the Waitemata Group, Auckland, is characterised, and the influence of microstructure in determining the geomechanics examined. Field geotechnical measurements of joint spacing and Schmidt Hammer rebound are related to geomechanical properties to determine controls on joint development and applicability of field index tests for soft materials. Samples studied are dominantly sandstones, with one conglomerate; all of which have a significant component of swelling clay minerals. Low bulk densities, high porosities and large void ratios are characteristic of the samples.

They vary from extremely weak, very low durability rocks to moderately: strong and durable materials. Extremely weak sandstones are highly deformable and undergo plastic deformation when loaded in compression. The stronger samples undergo strain softening and respond elastically to applied stresses prior to brittle failure. High softening factors indicate that compressive and tensile strengths are greatly reduced upon saturation.

All the study rocks have high proportions of sand and silt size material (≤ 95 %), and up to 10 % of < 2 μ m proportions; significant gravel size material only occurs in the conglomerate. Volcanic and detrital rock fragments are the dominant constituents in all samples, with abundant quartz, minor calcic plagioclase, and a variety of accessory minerals. The dominant clay is smectite with lesser amounts of illite, kaolinite, and mixed-layer clays.

Individual sand and silt grains are dominantly subrounded to subangular quartz, regular bricks of feldspar, and rods of rutile, and are often clay coated. Microaggregates and grains are combined into aggregates and assemblages, and in some cases macroassemblages, to form granular arrangements, which produce a network of interconnecting pores. The fabric of the rocks is characterised by discontinuous matrices. Fabric types range from skeletal to turbostratic, and arrangements range from tightly interlocking grains to loose granular structures. Clay micro aggregates are either flocculated or form welded FF honeycomb arrangements.

Strength and durability are not influenced by quantity, size, or type of clasts or minerals present; rather, it is the arrangement of individual components (and associated pore spaces) in the rock fabric which directly determines the geomechanical behaviour. Strong, durable samples have an abundance of clean grain to grain contacts, and few large clay aggregates. Clay microaggregates are arranged in welded FF arrangements, and pore space is restricted to micropores which resist water infiltration. Progressively weaker rocks are characterised by an increase in clay coated grains, clay aggregates, and clay connectors (which form weak links for stress transmission), and interconnecting pores at all levels in the fabric. In the weakest rock macroassemblages of clay coated grains, and open flocculated smectitic aggregates connected by point contacts, produce a network of macropores, allowing easy access of water which flocculates clays into weaker states by reducing bonding and cohesion.

Schmidt rebound values in the field do not provide a useful indication of either compressive or tensile strength of these rocks. The rebound values do, however, correlate well with laboratory determined dynamic elasticity values, suggesting that the instrument should be used in the field to predict rock elasticity and not strength.

Joint spacing within the rock units is related to elasticity with units capable of storing stress through plastic deformation having reasonably wide, uniformly spaced joints. Units which release stress through brittle fracture have closely spaced, and more complex joint systems.

year: 1992

title: Understanding the use of Māori and English in dual language picturebooks through a sociolinguistic lens

authors: Daly, Nicola

abstract: In this presentation I will explore the use of te reo Māori in English text in dual language picturebooks published in Aotearoa/New Zealand. A series of studies examining the frequency of Māori loanwords in children’s picturebooks (Daly 2007; Daly 2008; Macdonald & Daly, 2013) are presented showing that when books came out of a publishing company with a commitment to publishing Māori and Pasifika stories, the frequency of loanwords was much higher than in other contexts; but even when a survey of all picturebooks published in New Zealand between 1995 and 2005 was conducted, the frequency of loanwords was much higher than in previous studies of comparable literature, such as the New Zealand school journal (Macalister, 1999). Very few dual language picturebooks featuring Māori and English are produced in New Zealand (Daly 2016a; Daly 2016b). The synchronous or sequential format of having separate books for each language seems to be favoured. But it is in the parallel dual language format (where both languages are present in a single book) that the relative status of the two languages is evident. In the second part of the presentation the layout and comparative presentation of the two languages are explored in terms of size of font and order of languages, using a Linguistic Landscape framework (Landry & Bourhis, 1997). These uses of two languages within New Zealand children’s literature (both interlingual and dual language) are examined and considered in terms of Bell’s (1984) theory of Audience Design, considering whether writers and publishers of such literature are now catering for a wider and more bilingual audience and whether publishing such linguistically diverse material such linguistically diverse picturebooks may be contributing to the creation of a more bilingual society.

text: Understanding the use of Māori and English in dual language picturebooks through a sociolinguistic lens In this presentation I will explore the use of te reo Māori in English text in dual language picturebooks published in Aotearoa/New Zealand. A series of studies examining the frequency of Māori loanwords in children’s picturebooks (Daly 2007; Daly 2008; Macdonald & Daly, 2013) are presented showing that when books came out of a publishing company with a commitment to publishing Māori and Pasifika stories, the frequency of loanwords was much higher than in other contexts; but even when a survey of all picturebooks published in New Zealand between 1995 and 2005 was conducted, the frequency of loanwords was much higher than in previous studies of comparable literature, such as the New Zealand school journal (Macalister, 1999). Very few dual language picturebooks featuring Māori and English are produced in New Zealand (Daly 2016a; Daly 2016b). The synchronous or sequential format of having separate books for each language seems to be favoured. But it is in the parallel dual language format (where both languages are present in a single book) that the relative status of the two languages is evident. In the second part of the presentation the layout and comparative presentation of the two languages are explored in terms of size of font and order of languages, using a Linguistic Landscape framework (Landry & Bourhis, 1997). These uses of two languages within New Zealand children’s literature (both interlingual and dual language) are examined and considered in terms of Bell’s (1984) theory of Audience Design, considering whether writers and publishers of such literature are now catering for a wider and more bilingual audience and whether publishing such linguistically diverse material such linguistically diverse picturebooks may be contributing to the creation of a more bilingual society.

year: 2018