How long does the insect repellent remain effective

Assignment Help Mechanical Engineering

Reference no: EM13942658

A person applies an insect repellent onto an exposed area of A = 0.5 m² of their body. The mass of spray used is M = 10 grams, and the spray contains 25% (by mass) active ingredient. The inactive ingredient quickly evaporates from the skin surface.

(a) If the spray is applied uniformly and the density of the dried active ingredient is p = 2000 kg/m3, determine the initial thickness of the film of active ingredient on the skin surface. The temper- ature, molecular weight, and saturation pressure of the active ingredient are 32°C, 152 kg/kmol, and 1.2 X 10^-5 bars, respectively.

(b) If the convection mass transfer coefficient associated with sublimation of the active ingredient to the hydrogen in the glass fiber are DAB = 2.88 X 10^-15the air is hm

= 5 X 10^-3 m/s

Hydrogen diffusion into the fiber is undesirable, since it changes the spectral transmissivity and refractive index of the glass and can lead to failure of the detection system.

(a) Determine the average hydrogen concentration in an uncoated optical fiber, C, after 100 h of operation in the hydrogen environment.

(b) Determine the corresponding change in the refractive index, n, of the fiber. For vitreous silica, n = (1.6 X 10-3 m3/kmol) X C.

cient associated with the ingredient-skin interface is K = 0.05, and the mass diffusivity of the active ingredient in the skin is DAB = 1 X 10^-13m²/s, determine how long the insect repellent remains effective. The partition coefficient is the ratio of the ingredient density in the skin to the ingredient density outside the skin.

(c) If the spray is reformulated so that the partition coefficient becomes very small, how long does the insect repellent remain effective?

Reference no: EM13942658

Questions Cloud

What are the outlet air temperature : What are the outlet air temperature, the heat rate q, and pressure drop tip for these conditions - To illustrate the tradeoff between heat transfer rate and pressure drop considerations, calculate q and tip for diameters in the range from 0.1 to 0...

How does auteurist theory affect the way that films : How does auteurist theory affect the way that films are marketed? How does it affect the way that films are analyzed by critics and audiences?

Issue at the origin of the policy : Describe the issue at the origin of the policy and the conditions that surrounded it. When did it take place?

How did the national view of the chicago police department : How did the new community policing strategy fit with the need to increase the accountability of police officers and the decentralization of responsibility?

How long does the insect repellent remain effective : Determine the average hydrogen concentration in an uncoated optical fiber, C, after 100 h of operation in the hydrogen environment - how long does the insect repellent remain effective?

How does it fulfill the expectations of that genre : How does it fulfill the expectations of that genre? How does it play against these expectations?

Article by susan dymock : Using the article by Susan Dymock, complete the following. 1. What is the object of teaching comprehension strategies:

Is crime reduction more important than community relations : Is crime reduction more important than community relations? What are your suggestions for bridging the gap between crime reduction and community relations? How can the two be brought closer together?

Where gm gets away literally with murder : General Motors - http://www.youtube.com/watch?v=3fn9uw_y318 where GM gets away literally with murder? They were also bailed out by the taxpayers, and even now their CEOs are getting high salaries and raises

User Account

All Pages