Theoretical and experimental analysis of a horizontal planar Liquid-Vapour Thermal Diode (PLVTD)

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Abstract

Thermal diodes are unidirectional heat transfer devices, analogous to electrical diodes, which offer low resistance (thermal conductance) in one direction and high resistance (thermal insulation) in the other. Thermal diodicity has significant potential to improve the efficacy of a wide variety of heating and cooling devices. This paper presents pioneering work to experimentally measure the heat transfer characteristics of a 0.15 m 2 passive Planar Liquid-Vapour Thermal Diode (PLVTD). Prior work has typically examined much smaller devices aimed at micro-electronics cooling applications whereas the present work aims to improve understanding of larger scale devices for incorporation in solar collectors and multi-function climate control building envelopes. Such applications can facilitate local renewable energy generation (solar and ambient heat collection) and improve cooling system energy efficiency (passive heat rejection) in order to address the climate crisis by decarbonising built environment energy use. Experimental work involved a horizontally oriented PLVTD formed of two parallel isothermal plates with integral serpentine heat exchangers and external insulation. Plate, fluid, and ambient temperatures were controlled and measured to determine heat transfer coefficients under various temperature difference and heat flux operating scenarios in order to validate a simple one-dimensional lumped parameter model. Measured forward mode heat transfer 150 < U f < 500 W·m −2 K −1 combined with reverse mode insulation U r = 10 W·m −2 K −1 corresponds ς ≈ 88% diodicity at low condenser temperatures and fluxes (T 2 ≈ 15 °C and q/A ≈ 120 W∙m −2) and ς ≈ 96% at high condenser temperatures and heat fluxes (T 2 ≈ 60 °C and q/A ≈ 2800 W∙m −2). Forward mode performance increases with increasing heat flux and (to a lesser extent) with increasing operating temperature but is largely independent of PLVTD dimensions. Reverse mode performance is largely independent of heat flux and temperature but reduces (improves thermal insulation) with increasing cavity depth. The model has been used to show that a stainless steel PLVTD with x = 70 mm cavity can achieve U r = 2 W·m −2 K −1 with similar forward mode performance to the experimental prototype. Such a device would achieve diodicity of ς > 97% and be suitable for application in solar collectors and climate control building envelopes.

LanguageEnglish
Article number118660
Pages1-34
Number of pages34
JournalInternational Journal of Heat and Mass Transfer
Volume144
Early online date6 Sep 2019
DOIs
Publication statusPublished - 1 Dec 2019

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Diodes
Vapors
diodes
vapors
heat flux
Liquids
liquids
climate
Heat flux
solar collectors
thermal insulation
heat transfer
condensers
Climate control
insulation
Solar collectors
Thermal insulation
envelopes
Heat transfer
temperature

Keywords

  • Thermal diode
  • one-way heat flow
  • phase change
  • solar collector
  • heat rejection
  • Heat rejection
  • Solar collector
  • Phase change
  • One-way heat flow

Cite this

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title = "Theoretical and experimental analysis of a horizontal planar Liquid-Vapour Thermal Diode (PLVTD)",
abstract = "Thermal diodes are unidirectional heat transfer devices, analogous to electrical diodes, which offer low resistance (thermal conductance) in one direction and high resistance (thermal insulation) in the other. Thermal diodicity has significant potential to improve the efficacy of a wide variety of heating and cooling devices. This paper presents pioneering work to experimentally measure the heat transfer characteristics of a 0.15 m 2 passive Planar Liquid-Vapour Thermal Diode (PLVTD). Prior work has typically examined much smaller devices aimed at micro-electronics cooling applications whereas the present work aims to improve understanding of larger scale devices for incorporation in solar collectors and multi-function climate control building envelopes. Such applications can facilitate local renewable energy generation (solar and ambient heat collection) and improve cooling system energy efficiency (passive heat rejection) in order to address the climate crisis by decarbonising built environment energy use. Experimental work involved a horizontally oriented PLVTD formed of two parallel isothermal plates with integral serpentine heat exchangers and external insulation. Plate, fluid, and ambient temperatures were controlled and measured to determine heat transfer coefficients under various temperature difference and heat flux operating scenarios in order to validate a simple one-dimensional lumped parameter model. Measured forward mode heat transfer 150 < U f < 500 W·m −2 K −1 combined with reverse mode insulation U r = 10 W·m −2 K −1 corresponds ς ≈ 88{\%} diodicity at low condenser temperatures and fluxes (T 2 ≈ 15 °C and q/A ≈ 120 W∙m −2) and ς ≈ 96{\%} at high condenser temperatures and heat fluxes (T 2 ≈ 60 °C and q/A ≈ 2800 W∙m −2). Forward mode performance increases with increasing heat flux and (to a lesser extent) with increasing operating temperature but is largely independent of PLVTD dimensions. Reverse mode performance is largely independent of heat flux and temperature but reduces (improves thermal insulation) with increasing cavity depth. The model has been used to show that a stainless steel PLVTD with x = 70 mm cavity can achieve U r = 2 W·m −2 K −1 with similar forward mode performance to the experimental prototype. Such a device would achieve diodicity of ς > 97{\%} and be suitable for application in solar collectors and climate control building envelopes.",
keywords = "Thermal diode, one-way heat flow, phase change, solar collector, heat rejection, Heat rejection, Solar collector, Phase change, One-way heat flow",
author = "Adrian Pugsley and A Zacharopoulos and Jayanta Mondol and Mervyn Smyth",
year = "2019",
month = "12",
day = "1",
doi = "10.1016/j.ijheatmasstransfer.2019.118660",
language = "English",
volume = "144",
pages = "1--34",
journal = "International Journal of Heat and Mass Transfer",
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TY - JOUR

T1 - Theoretical and experimental analysis of a horizontal planar Liquid-Vapour Thermal Diode (PLVTD)

AU - Pugsley, Adrian

AU - Zacharopoulos, A

AU - Mondol, Jayanta

AU - Smyth, Mervyn

PY - 2019/12/1

Y1 - 2019/12/1

N2 - Thermal diodes are unidirectional heat transfer devices, analogous to electrical diodes, which offer low resistance (thermal conductance) in one direction and high resistance (thermal insulation) in the other. Thermal diodicity has significant potential to improve the efficacy of a wide variety of heating and cooling devices. This paper presents pioneering work to experimentally measure the heat transfer characteristics of a 0.15 m 2 passive Planar Liquid-Vapour Thermal Diode (PLVTD). Prior work has typically examined much smaller devices aimed at micro-electronics cooling applications whereas the present work aims to improve understanding of larger scale devices for incorporation in solar collectors and multi-function climate control building envelopes. Such applications can facilitate local renewable energy generation (solar and ambient heat collection) and improve cooling system energy efficiency (passive heat rejection) in order to address the climate crisis by decarbonising built environment energy use. Experimental work involved a horizontally oriented PLVTD formed of two parallel isothermal plates with integral serpentine heat exchangers and external insulation. Plate, fluid, and ambient temperatures were controlled and measured to determine heat transfer coefficients under various temperature difference and heat flux operating scenarios in order to validate a simple one-dimensional lumped parameter model. Measured forward mode heat transfer 150 < U f < 500 W·m −2 K −1 combined with reverse mode insulation U r = 10 W·m −2 K −1 corresponds ς ≈ 88% diodicity at low condenser temperatures and fluxes (T 2 ≈ 15 °C and q/A ≈ 120 W∙m −2) and ς ≈ 96% at high condenser temperatures and heat fluxes (T 2 ≈ 60 °C and q/A ≈ 2800 W∙m −2). Forward mode performance increases with increasing heat flux and (to a lesser extent) with increasing operating temperature but is largely independent of PLVTD dimensions. Reverse mode performance is largely independent of heat flux and temperature but reduces (improves thermal insulation) with increasing cavity depth. The model has been used to show that a stainless steel PLVTD with x = 70 mm cavity can achieve U r = 2 W·m −2 K −1 with similar forward mode performance to the experimental prototype. Such a device would achieve diodicity of ς > 97% and be suitable for application in solar collectors and climate control building envelopes.

AB - Thermal diodes are unidirectional heat transfer devices, analogous to electrical diodes, which offer low resistance (thermal conductance) in one direction and high resistance (thermal insulation) in the other. Thermal diodicity has significant potential to improve the efficacy of a wide variety of heating and cooling devices. This paper presents pioneering work to experimentally measure the heat transfer characteristics of a 0.15 m 2 passive Planar Liquid-Vapour Thermal Diode (PLVTD). Prior work has typically examined much smaller devices aimed at micro-electronics cooling applications whereas the present work aims to improve understanding of larger scale devices for incorporation in solar collectors and multi-function climate control building envelopes. Such applications can facilitate local renewable energy generation (solar and ambient heat collection) and improve cooling system energy efficiency (passive heat rejection) in order to address the climate crisis by decarbonising built environment energy use. Experimental work involved a horizontally oriented PLVTD formed of two parallel isothermal plates with integral serpentine heat exchangers and external insulation. Plate, fluid, and ambient temperatures were controlled and measured to determine heat transfer coefficients under various temperature difference and heat flux operating scenarios in order to validate a simple one-dimensional lumped parameter model. Measured forward mode heat transfer 150 < U f < 500 W·m −2 K −1 combined with reverse mode insulation U r = 10 W·m −2 K −1 corresponds ς ≈ 88% diodicity at low condenser temperatures and fluxes (T 2 ≈ 15 °C and q/A ≈ 120 W∙m −2) and ς ≈ 96% at high condenser temperatures and heat fluxes (T 2 ≈ 60 °C and q/A ≈ 2800 W∙m −2). Forward mode performance increases with increasing heat flux and (to a lesser extent) with increasing operating temperature but is largely independent of PLVTD dimensions. Reverse mode performance is largely independent of heat flux and temperature but reduces (improves thermal insulation) with increasing cavity depth. The model has been used to show that a stainless steel PLVTD with x = 70 mm cavity can achieve U r = 2 W·m −2 K −1 with similar forward mode performance to the experimental prototype. Such a device would achieve diodicity of ς > 97% and be suitable for application in solar collectors and climate control building envelopes.

KW - Thermal diode

KW - one-way heat flow

KW - phase change

KW - solar collector

KW - heat rejection

KW - Heat rejection

KW - Solar collector

KW - Phase change

KW - One-way heat flow

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U2 - 10.1016/j.ijheatmasstransfer.2019.118660

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JO - International Journal of Heat and Mass Transfer

T2 - International Journal of Heat and Mass Transfer

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SN - 0017-9310

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