title: Heat Transfer Enhancement in Heat Recovery Loops Using Nanofluids as the Intermediate Fluid

authors: Tarighaleslami, Amir Hossein

abstract: In this paper, the effect of replacing water with various nanofluids as the heat transfer media in an industrial Heat Recovery Loop (HRL) have been modelled. Generally, nanofluids are prepared by distributing a nanoparticle through a base fluid such as water. Suspended nanoparticles slightly affect the thermal and physical properties of the base fluid. Primarily nanoparticles are added to improve the fluid’s heat transfer characteristics by increasing its Reynolds number and thermal conductivity. Results show that by applying various HRL design methods and a nanofluid as an intermediate fluid, an increase in heat recovery is possible without the need for extra heat exchanger area and infrastructure. With the addition of 1.5 vol.% CuO nanoparticles to the HRL fluid using constant temperature storage method, heat recovery from liquid-liquid heat exchangers increases between 5 % and 9 %. In the case of air-liquid exchangers, the air-side heat transfer coefficient limits the impact of using a nanofluid. In other cases, the duty available from the process stream, such as a condenser, significantly restricts the heat transfer benefit of using a nanofluid. Alternative to increasing heat recovery, results show that applying a nanofluid in the HRL design phase enables heat exchanger area to decrease significantly for liquid-liquid matches.

text: Heat Transfer Enhancement in Heat Recovery Loops Using Nanofluids as the Intermediate Fluid In this paper, the effect of replacing water with various nanofluids as the heat transfer media in an industrial Heat Recovery Loop (HRL) have been modelled. Generally, nanofluids are prepared by distributing a nanoparticle through a base fluid such as water. Suspended nanoparticles slightly affect the thermal and physical properties of the base fluid. Primarily nanoparticles are added to improve the fluid’s heat transfer characteristics by increasing its Reynolds number and thermal conductivity. Results show that by applying various HRL design methods and a nanofluid as an intermediate fluid, an increase in heat recovery is possible without the need for extra heat exchanger area and infrastructure. With the addition of 1.5 vol.% CuO nanoparticles to the HRL fluid using constant temperature storage method, heat recovery from liquid-liquid heat exchangers increases between 5 % and 9 %. In the case of air-liquid exchangers, the air-side heat transfer coefficient limits the impact of using a nanofluid. In other cases, the duty available from the process stream, such as a condenser, significantly restricts the heat transfer benefit of using a nanofluid. Alternative to increasing heat recovery, results show that applying a nanofluid in the HRL design phase enables heat exchanger area to decrease significantly for liquid-liquid matches.

year: 2015-08-27

title: Speed control with low armature loss for very small sensorless brushed DC motors

authors: Scott, Jonathan B.

subjects: DC motor drives

abstract: A method for speed control of brushed dc motors is presented. It is particularly applicable to motors with armatures of less than 1 cm3. Motors with very small armatures are difficult to control using the usual pulsewidth-modulation (PWM) approach and are apt to overheat if so driven. The technique regulates speed via the back electromotive force but does not require current-discontinuous drives. Armature heating in small motors under PWM drive is explained and quantified. The method is verified through simulation and measurement. Control is improved, and armature losses are minimized. The method can expect to find application in miniature mechatronic equipment.

text: Speed control with low armature loss for very small sensorless brushed DC motors A method for speed control of brushed dc motors is presented. It is particularly applicable to motors with armatures of less than 1 cm3. Motors with very small armatures are difficult to control using the usual pulsewidth-modulation (PWM) approach and are apt to overheat if so driven. The technique regulates speed via the back electromotive force but does not require current-discontinuous drives. Armature heating in small motors under PWM drive is explained and quantified. The method is verified through simulation and measurement. Control is improved, and armature losses are minimized. The method can expect to find application in miniature mechatronic equipment.

year: 2009

title: A case study of using the He Pikinga Waiora Implementation Framework: Challenges and successes in implementing a twelve-week lifestyle intervention to reduce weight in Māori men at risk of diabetes, cardiovascular disease and obesity

authors: Oetzel, John G.

subjects: Science & Technology

abstract: BACKGROUND: Māori men have stark health inequities around non-communicable diseases. This study describes the case of a partnership attempting to develop and implement a culturally centred intervention through a collaborative partnership to potentially address the inequities. In particular, the partnership followed a participatory, co-design approach using the He Pikinga Waiora (HPW) Implementation Framework; the study presents lessons learnt in addressing health inequities following this framework. METHODS: The partnership involved a university research team and a Māori community health provider. They engaged with other stakeholders and several cohorts of Māori men through a co-design process to adapt a 12-week lifestyle intervention. The co-design process was documented through meeting notes and interviews with partners. Two cohorts participated in separate single group pre-intervention/post-intervention designs with multi-method data collection. Key outcome measures included weight loss, self-reported health, physical activity, and nutrition. Post-intervention data collection included qualitative data. RESULTS: The co-design process resulted in a strong and engaged partnership between the university team and the provider. There were significant challenges in implementing the intervention including having two additional partner organisations dropping out of the partnership just after the initial implementation phase. However, a flexible and adaptable partnership resulted in developing two distinct lifestyle interventions run with 32 Māori men (in two different cohorts of 8 and 24). All but one in the first cohort completed the programme. The first cohort had a modest although statistically insignificant improvement in weight loss (d = 1.04) and body mass index (BMI; d = 1.08). The second cohort had a significant reduction in weight loss (d = 1.16) and BMI (d = 1.15). They also had a significant increase in health-related quality of life (d = 1.7) and self-rated health (d = 2.0). CONCLUSION: The HPW Framework appears to be well suited to advance implementation science for Indigenous communities in general and Māori in particular. The framework has promise as a policy and planning tool to evaluate and design interventions for chronic disease prevention in Indigenous communities. Despite this promise, there are structural challenges in developing and implementing interventions to address health inequities. TRIAL REGISTRATION: Retrospectively registered, Australia New Zealand Clinical Trials Registry, ACTRN12619001783112.

text: A case study of using the He Pikinga Waiora Implementation Framework: Challenges and successes in implementing a twelve-week lifestyle intervention to reduce weight in Māori men at risk of diabetes, cardiovascular disease and obesity BACKGROUND: Māori men have stark health inequities around non-communicable diseases. This study describes the case of a partnership attempting to develop and implement a culturally centred intervention through a collaborative partnership to potentially address the inequities. In particular, the partnership followed a participatory, co-design approach using the He Pikinga Waiora (HPW) Implementation Framework; the study presents lessons learnt in addressing health inequities following this framework. METHODS: The partnership involved a university research team and a Māori community health provider. They engaged with other stakeholders and several cohorts of Māori men through a co-design process to adapt a 12-week lifestyle intervention. The co-design process was documented through meeting notes and interviews with partners. Two cohorts participated in separate single group pre-intervention/post-intervention designs with multi-method data collection. Key outcome measures included weight loss, self-reported health, physical activity, and nutrition. Post-intervention data collection included qualitative data. RESULTS: The co-design process resulted in a strong and engaged partnership between the university team and the provider. There were significant challenges in implementing the intervention including having two additional partner organisations dropping out of the partnership just after the initial implementation phase. However, a flexible and adaptable partnership resulted in developing two distinct lifestyle interventions run with 32 Māori men (in two different cohorts of 8 and 24). All but one in the first cohort completed the programme. The first cohort had a modest although statistically insignificant improvement in weight loss (d = 1.04) and body mass index (BMI; d = 1.08). The second cohort had a significant reduction in weight loss (d = 1.16) and BMI (d = 1.15). They also had a significant increase in health-related quality of life (d = 1.7) and self-rated health (d = 2.0). CONCLUSION: The HPW Framework appears to be well suited to advance implementation science for Indigenous communities in general and Māori in particular. The framework has promise as a policy and planning tool to evaluate and design interventions for chronic disease prevention in Indigenous communities. Despite this promise, there are structural challenges in developing and implementing interventions to address health inequities. TRIAL REGISTRATION: Retrospectively registered, Australia New Zealand Clinical Trials Registry, ACTRN12619001783112.

year: 2020