Body fluids ambient temperature

Most metalworking fluids are buffered at about pH 9.0-9.5. Any biocide used must have long-term stability and be efficacious at these pH ranges. In addition to this, a degree of thermal stability is desirable. The main body of diluted metalworking fluid will maintain at a relatively constant temperature, usually about the ambient temperature. The product concentrate may be subject to significant temperature variation depending on how it is stored and the part of the world it is destined for. 

Ambient temperature affects the composition of body fluids. Acute exposure to heat causes the plasma volume to expand by an influx of interstitial fluid into the intravascular space, and by reduction of glomerular filtration. The. plasma protein concentration may decrease by up to 10%. Sweating may cause salt and water loss, but usually there are no changes in the plasma sodium and chloride concentrations. Plasma potassium concentration may decrease by as much as 10% as potassium is taken up by the cells. If sweating is extensive, hemoconcentration rather than hemodilution may occur. 

To focus our subsequent discussion, let us begin by considering the problem of heat removal from a body of arbitrary shape that is immersed in a fluid that is undergoing a uniform motion of magnitude U, relative to the body. The situation is illustrated in Fig. 9-1. We shall suppose that the fluid has an ambient temperature far from the body. Furthermore, we assume, for simplicity, that the body is heated in such a way that its... 

Figure 9-1. A schematic representation of a body of arbitrary shape and constant surface temperature, To, immersed in a fluid of constantproperties, />, //., Cp, k, and ambient temperature Trxj that undergoes a uniform motion of magnitude relative to the body. The body...

The conditions (1 l-7a) and (1 l-7c) correspond to the assumption that the surface of the body is heated (or cooled) to a constant temperature T0 beyond a certain position denoted as x. Upstream of x, the body is not heated. Hence, at steady state in the present boundary layer limit, both the body surface and the fluid remain at the ambient temperature T,x, for x < x. If the body is heated over its whole surface, then x = 0. In this case, the leading edges of the thermal and momentum boundary layers are coincident. 

Of course, (12-164) is still exact, and the system of equations (12-164), (12-160), and (12-161) is no easier to solve than the original system of equations. To produce a tractable problem for analytic solution, it is necessary to introduce the so-called Boussinesq approximation, which has been used for many of the existing analyses of natural and mixed convection problems. The essence of this approximation is the assumption that the temperature variations in the fluid are small enough that the material properties p, p, k, and Cp can be approximated by their values at the ambient temperature Tq, except in the body-force term in (12-164), where the approximation p = po would mean that the fluid remains motionless. 

We have already noted that the general class of flows driven by buoyancy forces that are created because the density is nonuniform is known as natural convection. If we examine the Boussinesq approximation of the Navier-Stokes equations, (12-170), we can see that there are actually two types of natural convection problems. In the first, we assume that a fluid of ambient temperature 71, is heated at a bounding surface to a higher temperature I. This will produce a nonuniform temperature distribution in the contiguous fluid, and thus a nonuniform density distribution too. Let us suppose that the heated surface is everywhere horizontal. Then there is a steady-state solution of (12-170) with u = 0, and the body-force terms balanced by a modification to the hydrostatic pressure distribution, such that... 

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