Page 17 - Science Focus (Issue 017)

most stable shapes [5]. Meanwhile, a semi-circled arch thermal insulator. In addition, snow is a very reflective
contains certain sites of higher tension (as indicated in material which can reflect heat inwards in the form of
Figure 1), in which the snow crystals are pulled apart, infra-red radiation. Hence, the body heat radiated from
causing the igloo to collapse easily with a little force [5] a person inside the igloo can be retained very efficiently,
as the heat loss through conduction and radiation is
minimized. As expected, the temperature inside the
igloo can easily be raised with more people, or by using
oil lamps or candles to increase the heat release.
Other than conduction and radiation, Inuits also
take advantage of their knowledge of the third method
of heat transfer, convection, to prevent heat loss. You
may have heard of the fact that warm air rises, and
Figure 1. Force trend arrows showing the resultant force cold air sinks. With this phenomenon in mind, igloos are
direction in a semi-circled shape with blocks of high tension constructed with a sunken entrance tunnel, with areas
and instability shown in white (left), and a parabolic arch of snow dug down, and raised sleeping and living
shape (right) [5]. platforms [2, 7-8]; thus, the heavier cold air sinks towards
圖一 箭咀表示在均勻半圓（左；白色雪磚為高張力的不穩定雪磚）和拋 the lower entrance area, and the upper area, where
物線狀（右）的拱形中合力的方向 [5]。
the Inuits sleep and reside in, are surrounded by warmer
How Does Igloo Keep Us Warm? air. In addition, the sunken tunnel can also prevent chill
wind and snow from blowing in directly [2, 3, 8].
Now that we know how an igloo is built, but how Collectively, all these factors could lead to an indoor
exactly does the snow keep us warm? temperature of close to 15 C inside the igloo [1, 7-8]
o
First we need to clear a misconception — the terms even with an outdoor temperature of around –45 C!
o
“hot” and “cold” are relative, simply used to describe With the laws of physics at play in the
our perception as a result of heat transfer; (at most of igloo’s architecture, one can live in a
the time) we feel cold when the body loses heat to the comfortable and cozy snow home in the
surroundings [6]. Therefore, our goal is to create a space freezing Arctic.
that is thermally insulated from the freezing environment. 1 The two groups of people, Inuit and Yupik, are
Igloos are perfect structures for preserving heat. This often referred as Eskimo. Nevertheless, the
is primarily due to the property of compressed snow term “Eskimo” may be considered pejorative
blocks: they are filled with air pockets and contain up because it is associated with the meaning of
to 95% of trapped air [2], making them an excellent “eater of raw meat.” [9]

o
冰屋怎樣使我們溫暖？ 綜合來說，即使戶外的溫度約為 –45 C，這些方面的措
o
現在我們知道冰屋是如何搭起的，但它實際上怎樣能使 施都可以令冰屋內部有著接近 15 C 的氣溫 [1, 7-8]！
我們保持溫暖？ 冰屋的建築正是因為有著在物理定律上的各種考量，才
首先我們要先釐清一個誤解 —「冷」、「熱」這兩個詞是 能讓人即使在冰封的北極，亦能住進一個舒適愜意的家。
相對的，用來描述熱傳遞（heat transfer）為我們所帶來的 1 因紐特人（Inuit）和尤皮克人（Yupik）這兩群人通常都被統稱為愛斯基摩
感覺：（在大多數情況下）當身體的熱流失到四周環境時，我 人（Eskimo）。可是，愛斯基摩人這個詞語的本意為「嗜生肉的人」，因此有
時會被視為帶有貶義的稱呼 [9]。
們感到冷 [6]。因此，我們的目標是製造一個冷熱上絕緣的空
間，把我們與寒冷的環境隔開。 References 參考資料：
[1] DK Publishing. (2003). How People Live. New York, NY: DK Publishing, Inc.
冰屋是把熱留住的絕佳結構。這主要是因為那些壓得 [2] Greenway, T. (2019). How Does an Igloo Work & Do They Keep You
實實的雪磚：它當中有很多氣囊把空氣困住，一塊雪磚的空 Warm? Retrieved from https://www.transun.co.uk/blogs/how-does-
an-igloo-work.
氣含量甚至能高達 95% [2]，使它們成為優良的熱絕緣體。 [3] Hoyt, A. (2008). How Igloos Work. Retrieved from https://people.
此外，雪是一種反射性強的物料，能把熱以紅外線的形式向 howstuffworks.com/igloo3.htm.
冰屋內反射。因此，從人體散發的熱能被非常有效地留住， [4] Fecht, S. (2017). Want to build an igloo? Here's how. Retrieved from
https://www.popsci.com/how-to-build-an-igloo/.
經傳導和輻射散失的熱因而大大減少。與我們所料的一樣， [5] Yankielun, N. E. (2007). How to Build an Igloo, And Other Snow
Shelters. New York, NY: Norton.
更多人在冰屋裡面，以及在冰屋裡面使用油燈和蠟燭都能 [6] Science Buddies. (2015). Cold or Warm, Can We Really Tell? Scientific
輕易地使冰屋內的溫度上升，因為釋放更多熱。 American. Retrieved from https://www.scientificamerican.com/
article/cold-or-warm-can-we-really-tell/
除了傳導和輻射，因紐特人還善用了他們對熱傳遞的第 [7] Hosoe, I., Murakami, S., Saotome, T., Mizuishi, T., & Fujii, A. (2005).
三個方法 — 對流的知識來減少熱的流失。你可能已經知道 Evaluation of Indoor Environment in Vernacular Dwellings –
Numerical Analysis of the Igloo by CFD –. Paper presented at the
熱空氣會上升，冷空氣會下降的事實。因紐特人亦深明這個 2005 World Sustainable Building Conference, Tokyo. Retrieved from
https://www.irbnet.de/daten/iconda/CIB3909.pdf.
道理，因此他們會在入口處把地面的雪挖走，建造一條比地 [8] Delgado, J. M. P. Q., Martinho, J. C., Vaz Sá, A., Guimarães, A. S.,
& Abrantes, V. (2019). Introduction. In Thermal Energy Storage with
面稍低的隧道作為入口，也會把睡覺和活動的地方建在一個 Phase Change Materials — A Literature Review of Applications
比地面稍高的位置 [2, 7-8]，令較重的冷空氣向較低的入口 for Buildings Materials (pp. 1-8). Cham, Switzerland: Springer
International Publishing.
處下沉，他們睡覺和居住的上層則被暖空氣所包圍。另外，下 [9] Alaska Native Language Center. (n.d.). Inuit or Eskimo: Which name
沉的隧道還可以避免刺骨的寒風直接吹進屋內 [2, 3, 8]。 to use? Retrieved from https://www.uaf.edu/anlc/resources/inuit_or_
eskimo.php.
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