離心機原理

The centrifugal force F experienced by a small volume of liquid V in a test-tube of cross-sectional area A in a centrifuge is given by,

F = (pV)r.w^2
where p is the density of liquid and r is the radius of revolution of the volume of liquid.

Hence, pressure P produced = F/A = (pV)r.w^2/A = p(V/A)r.w^2
since V/A = L, the height of liquid in the tes-tube
P = pL.rw^2
Thus, pressure P increases with r

The presure gradient established in the liquid because of centrifugal force
= dP/dr = pLw^2
which is a constant

Hence, for particulates (with higher density p) in suspension in the liquid, they will experience a higher pressure gradient, and hence will be "thrown" to the end of the test tube by the centrifuge.

离心机是利用离心力，分离液体与固体颗粒或液体与液体的混合物中各组分的机械。
离心机主要用于将悬浮液中的固体颗粒与液体分开；或将乳浊液中两种密度不同，又互不相溶的液体分开(例如从牛奶中分离出奶油)；它也可用于排除湿固体中的液体，例如用洗衣机甩干湿衣服；特殊的超速管式分离机还可分离不同密度的气体混合物；利用不同密度或粒度的固体颗粒在液体中沉降速度不同的特点，有的沉降离心机还可对固体颗粒按密度或粒度进行分级。