Category Archives: Publications

publication news

Forrest giving WeLL seminar at Berkeley CBE – Rethinking Radiant

Rethinking Radiant with CHAOS: Reflecting thoughts for Transparent research Emitting new ideas

Talk Abstract (12:15-1:30 2/6):  As the director of CHAOS (Cooling and Heating for Architecturally Optimized Systems) Lab at Princeton who is starting a short sabbatical until April at CBE I will try to give an overview of research and then drill into topics of common interest and debate.  I will present a brief overview of the work we have been doing the past 5 year (including some discoveries of Harrison Fraker’s past) and then zoom in on our current work on radiant systems. CHAOS originated as fun acronym, but also refers a consideration of system entropy to generate novel thermal systems and architectures. Through that thrust we are researching three primary areas: 1. Deeper geothermal 2. Liquid desiccants, and 3. Radiant systems and sensors. I will attempt to magically weave the relationships of those topics together and then focus on radiant systems.

Workshop (2pm-4pm 2/6): Between 3 and 5 CHAOS researchers will be in town next week returning from Singapore and visiting from Princeton with SMART sensor in tow. After the talk we plan to have an informal workshop. We will plan to start around 2pm for those that might be busy for the talk but interested in the workshop. Meet in the large conference room. The workshop will include a detailed overview of MRT calculations and measurement systems, and also the thermal comfort history and models we have reviewed. We will also discuss IoT hardware we have used for sensor backbone and prototyping infrastructure we have leveraged. Data management practices the database and REST-API systems we have setup on various platforms will be reviewed

CHAOS Participants include:
Eric Teitelbaum: Princeton PhD candidate (defending winter 2019), leader and constructor of Cold Tube in Singapore, SMART co-inventor and CSO of Hearth Labs spinoff
Nicholas Houchois: Researcher, co-inventor and leader of SMART development, CEO of Hearth Labs spinoff
Dr. Kianwee Chen: ETH Phd previously with MIT SMART, now Andlinger Center postdoctoral fellow with CHAOS lab.
Hongshan Guo (remote): Princeton PhD candidate (defending spring 2019), human body exergy modeling and research, coaxial geothermal borehole modeling, and urban radiant heat exchange and sensing.
Mauricio Lloyola Vergara (remote): Princeton PhD candidate (defending spring 2020), Post occupancy evaluation of IEQ and architectural spatial quality compared to proposed use and informed by IoT sensing techniques
Dorit Aviv (Remote): Asst Prof. U-Penn, Princeton PhD candidate (defending spring 2020): Surface geometry and form relating to radiant and evaporative surface heat and mass transport for experimental pavilions and architectures.

Summary with links to papers and references
The CHAOS lab has been working on a series of project exploring radiant heat transfer leveraging unconventional methods of reflection, transparency and emissivity of materials. These include architectural pavilions like the Thermoheliodome (EnB paper) and review of measurement methods like the black globe (EnB paper). This also includes the development of a 3D radiant heat exchange “SMART” Sensor (Princeton news). In parallel to the SMART sensor development we have built up significant expertise in IoT sensor design and construction. We have used those expertise to build deployable air quality sensors motivated by our bias toward radiant systems that air should be for breathing, not heating and cooling. Last year we published a paper on the potential of these inexpensive distributed sensors to spatially define the sources of pollutants throughout all aspects of a building’s ventilation systems and spaces.

Most recently on January 18th we launched the ColdTube in Singapore, an outdoor radiant cooling pavilion in Singapore as reported by Today. It is a collaboration between Berkeley (Jovan Pantelic), ETH (Arno Schlueter), UBC (Adam Rysanek), and Princeton (CHAOS lab). I will present the most recent findings including new questions they present regarding the ability to mitigate condensation with transparent membranes and also decouple convection from radiant exchanges. Our ASR paper just came out last week in the journal where the original concept was published in 1963. In this context there are also new questions about the validity of black globe measurements, which initial results show are incapable of measuring MRT more than 2.5K below the ambient temperature. This relates to many assumptions that have been made about radiant heat transfer and thermal comfort, and to what I believe is a commonly held false assumption that MRT cannot be significantly shifted from air temperature. In addition, as shown in our Singapore prototype, we can create environments with nearly zero convective heat exchange with the body while maintaining >100W/m2 of heat dissipation. We are interested in expanding building environmental analysis beyond empirical comfort boxes on psychrometric charts to realtime management of Watts of heat exchange with occupants by all means of conditioning. As the SMART sensor has the capability of also sensing occupancy and skin temperature of occupants, one of the future goals is to try to understand if and how indirect feedback on metabolic rate and thermal state might be generated and used to directly manage the Watts exchanged with occupants for a truly human-centric control. Ideally these last provocations will provide for plenty of discussion and lead into the workshop in the afternoon for those who are interested with the SMART sensor and my researchers who are visiting.

 

New article on non-condensing radiant panel experiments in Architectural Science Review

Revisiting radiant cooling: condensation-free heat rejection using infrared-transparent enclosures of chilled panels

Accepted 09 Dec 2018,  Published online: 31 Jan 2019

ABSTRACT

In this study, we enhance the understanding and design of a radiant cooling technology for outdoor comfort in tropical climates, originally proposed by R.N. Morse in 1963, in this journal. We investigate a type of radiant cooling methodology whereby the cold temperature source is physically separated from the outdoor environment by an insulated enclosure using a membrane transparent to infrared radiation. The enclosure isolates the radiant cooling surface from ambient conditions, allowing the radiant surface to be cooled significantly below ambient dew point temperatures without incurring condensation. For this new study, a Fourier Transform Infrared (FTIR) Spectroscopy analysis on three candidate membrane materials is undertaken and a prototype experimental test panel is fabricated. Our study shows that for a 5°C chilled panel temperature, the exterior membrane surface temperature reaches 26°C in a 32°C / 70% RH environment resulting in an effective mean radiant temperature of 15.8°C. These results provide new evidence in support of Morse’s original proposal, that such panels could provide significant radiant cooling without condensation in humid environments. Radiant cooling products based on the studied technology may offer an ability to provide thermally comfortable conditions in hot environments without the energy required for dehumidification.

https://www.tandfonline.com/doi/full/10.1080/00038628.2019.1566112