Author: chen.fz@otm.sg

Exhibition in WSH Forum on Heat Stress Management 2023

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Related instruments Thermal comfort

OTM exhibited in WSH Forum on Heat Stress Management 2023 (25/05/2023, NUS Shaw Foundation Alumni House Auditorium), with the following two instruments exhibited:

  • HD32.3TC handheld instrument for WBGT measurement; key features:
    • With a large color touchscreen
    • Probes are interchangeable for various thermal comfort and micro-environment measurements
    • High accuracy
  • HD35EDWWBGT wall-mounted instrument for WBGT measurement; key features:
    • For long-term WBGT monitoring (up to 500 ml water capacity for the natural wet bulb temperature probe)
    • Suitable for outdoor installation
    • With a wireless data logger and it is possible to configure it with cloud connectivity
    • High accuracy

Shown below is a photo of our booth:

We are grateful for the exhibition opportunity and booth setup assistance provided by WSH Council and MOM, and also the exhibition items provided by Delta OHM.

Our instrument: portable spectrophotometer

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We are a Singapore-based third-party test laboratory, providing lab test services of material optical & thermal properties. We use Konica Minolta CM-2500d portable spectrophotometer, with the following key information.

Key specifications

  • Spectral range: 360 nm – 740 nm
  • Integrating sphere size: 52 mm
  • Both specular component included (SCI) and specular component excluded (SCE) modes are supported
  • For both in-lab and on-site measurements

Instrument for outdoor thermal comfort measurement (with solar panel and cloud service)

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Related instruments Temperature & humidity, Air speed & wind, Thermal comfort

Shown below is an instrument integrated by OTM for outdoor thermal comfort measurement:

Below are the key features of the system:

  • Four quantities are measured: air temperature, relative humidity, airflow speed and globe temperature
  • Data logger included
  • With 4G connectivity and cloud service
  • With solar panel
  • Suitable for outdoor 24×7 monitoring
  • The height of the stand is adjustable in the range of 0.9 m to 1.5 m

Shown below is a screenshot of the cloud service portal:

Listed below are the key components in the systems:

Apparent thermal conductivity of multiple layers of coatings

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We have a post on the measurement of thin paint and coating thermal conductivity with the ASTM D5930 method. Many surfaces are coated with multiple layers of coatings. How to determine the apparent thermal conductivity of such multilayer coating systems?

The method described in the post is only applicable to one single layer of coating. For a surface coated with two or more layers of coatings, the method can only measure the top layer, but cannot determine the apparent thermal conductivity of multiple layers.

To determine the apparent thermal conductivity, the calculation method needs to be used. In this post, we use a two-layer coating system as an example:

  1. Measure the thermal conductivity of each layer individually (k1 and k2). Note: the samples need to be prepared individually too, as the method can measure the top layer only.
  2. Calculate the overall thermal resistance: R = d1/k1 + d2/k2, where d1 and d2 are the thickness of each layer.
  3. Calculate the apparent thermal conductivity: k = (d1 + d2)/R

For the calculation of the overall thermal resistance, our online ETTV U-value calculator can be used. The R-value result reported is the overall thermal resistance of all layers in the system.

Are the test methods for glass optical & thermal properties applicable to transparent plastic sheets?

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Related services Glass optical & thermal properties

As an alternative to glasses, several transparent plastic materials are utilized as window glazing panels. Transparent polycarbonate sheets and transparent acrylic sheets are two examples of such transparent plastic materials.

Can the standard NFRC/EN/ISO glass test methods still be employed to determine the optical & thermal properties of such transparent plastic materials?

The NFRC/EN/SIO glass test methods are for glazing materials, which are not limited to glasses. Plastics are a type of glazing material. Transparent plastic sheets can be tested by the NFRC/EN/ISO methods when the following conditions are met:

  1. With specular transmission and reflection only: materials with significant diffuse transmission/reflection are out of the scope (for example, frosted glasses, glasses with ceramic frits, and hazy plastic sheets).

    Note: in the latest NFRC methods (2020 version), diffuse materials are supported, but our lab is not ready to test such diffuse materials.
  2. Homogenous and flat sheet: corrugated plastic sheets and double-wall (multiple-wall) polycarbonate sheets are out of the scope.
  3. Without far-infrared transmission: plastic sheets with significant far-infrared transmission in the 5 µm to 50 µm range are out of the scope.

    Note: in the NFRC methods, it is possible to test materials with far-infrared transmission, but our lab is not ready to test such materials.

In principle, the scope of the NFRC/EN/ISO glass optical & thermal property test methods is based on the optical characteristics, but not on the material type. Transparent plastic sheets with the same optical characteristics as transparent glasses are within the scope.

Class A albedometer with data logger and tripod

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Related instruments Pyranometers, Weather stations, Wireless & web data loggers

We recently supplied an ISO 9060 spectrally flat Class A albedometer with a data logger and tripod to a customer in Singapore. Shown below are a photo of the system and a screenshot of the data logging software.

Listed below are the components in the system:

Can my material comply with BCA daylight reflectance requirements?

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Related services Daylight reflectance

The requirements on daylight reflectance by BCA are available in this circular dated 27/06/2016. Please refer to Section P.3.2 of the document (pages 5-6) for the requirements.

Below is a flowchart prepared by us for your easy reference:

For a specific scenario, you may click one of the blocks below for more elaborations.

My material is glass

For glasses, the requirement is that the daylight reflectance shall be less than 20%.

Please note the following:

  • For glasses, the concept of total/diffuse/specular daylight reflectance is not applicable, as glass is a material with specular reflection only (without diffuse reflection).
  • Daylight reflectance is also called visible light reflectance in some contexts. The “visible light reflectance, front” result in our glass test report is the same as the daylight reflectance result.
My material is not glass and is installed on a facade or horizontal/low-slope roof

For non-glass materials installed on facades or horizontal/low-slope roofs, the requirement is that the specular daylight reflectance shall be less than 10%.

Please note the following:

  • Specular daylight reflectance is also called specular reflectance in some contexts. They are the same.
  • Low-slope roof refers to a roof with less than 20 degrees of inclination angle (a horizontal roof is with 0 degrees of inclination angle).
My material is not glass and is installed on a steep-slope roof

For non-glass materials installed on steep-slope roofs, the requirement is that the total daylight reflectance shall be less than 20%.

Please note the following:

  • Total daylight reflectance is also called daylight reflectance in some contexts. They are the same.
  • Steep-slope roof refers to a roof with greater than 20 degrees of inclination angle (a horizontal roof is with 0 degrees of inclination angle).