To the Editor: I would like to commend the American car manufacturers for their success in the field, to be ahead of their counterparts from Japan, Italy, Germany, and elsewhere with the introduction of the latest designs in vehicles. It is a good achievement.

To always be ahead, they must consider introducing safer vehicles for use. It is high time we see designs that incorporate fire-resistant materials for the interiors of the cars. This would reduce the incidence of fire gutting the vehicle rapidly during
an accident.

I also call on American manufacturing industries to consider extending their plants to other continents including Africa, to explore the rich talents of African engineers.

Safe Engi-neering
John Mc Cabe
Santa Clara, Calif.

To the Editor: It has been gratifying to read a number of recent letters that acknowledge there is a sickness in the engineering world. I recently received my B.S. in mechanical engineering from an accredited school and I have been amazed by my short list of options. The outsourcing of entry-level jobs has left few opportunities available within the engineering field.

To those who still believe in career fairs, I challenge them to open up their eyes and see the fairs for what they have become: advertisements akin to billboard ads and staffed by those who don't know how to talk to an engineer. They no longer accept resumes, but instead point you to their Web page where yours can be lost with the thousands of others.

The few companies who do employ recent graduates hire in large numbers, creating a "meat farm" that often results in nothing but overworked, underpaid young people with short engineering careers.

What we lack in experience we more than make up for in focus and enthusiasm.

Editor's Note: The writer told us that since he sent this letter, he has taken a job as a mechanical technician after a 4 1/2-month job search.

To the Editor: When I read the letter from Sidney Goodman in the July 2005 issue of Mechanical Engineering, I was astounded that a trained engineer in analytical thought would make a statement that no-fly zones should be put up around the country's nuclear power plants.

Initially after 9/11, no-fly zones, called TFRs (temporary flight restrictions), were ordered around all nuclear power plants. Correctly so, they have been dropped in recognition that a TFR does not protect anything unless it is ringed by antiaircraft missiles and guns. Shooting down a few vacationing families and airliners that accidentally flew over the plant would be about the only result. A suicide attack from the air would take place within a matter of seconds, but would do little damage to the hardened systems of a nuclear power plant that could not be quickly repaired.

Goodman states that the 9/11 terrorists flew over the Indian Point nuclear plant. If their target had been the nuclear plant, a TFR would have had the same effect as a big "STOP" sign.

Let's leave fruitless gesturing to the news media and politicians. We all should expect more out of engineers.

To the Editor: In the Technology Focus article "Ducts Without Sweat" in the April 2005 issue, John Kluber of Kluber Skahan & Associates makes several claims regarding steam absorbers that deserve further clarification. His quotation "...steam absorbers are about half the cost of refrigerant chillers..." seems an exaggeration.

A steam absorber may be slightly less expensive than an electric chiller of the same cooling capacity. However, the steam absorber must reject twice the heat of the electric chiller. Therefore, the condenser water pumps, cooling tower, and piping for the steam absorber will be twice the size of the same-capacity electric chiller. The increased expense of the condenser water systems will, in general, more than exceed any first cost advantage that the absorber may have against an electric chiller.

Kluber Skahan & Associates designed a chilled water ventilation system with fabric ductwork for this Oswego, Ill., high school.

Steam absorbers also require a large minimum condenser water rate regardless of the building cooling demand. Therefore, condenser water pumps for absorbers cannot be slowed down to save electric energy during low demand periods that constitute the majority of cooling for most buildings. The large pumping energy requirements of absorbers make them difficult to justify, even in the case of cogeneration where the waste heat used by the absorber is almost free. At low building loads, a high-efficiency variable speed centrifugal chiller can actually provide more cooling per dollar than an absorber using almost free waste heat (high-temperature water, not steam). Given an almost free steam source, an absorber could be competitive with a variable speed centrifugal chiller at low loads and have an advantage at high loads. However, if you must pay to generate the steam, then the absorber makes no economic sense.

In addition to the capital and operating expenses, absorbers are considerably heavier than electric centrifugal chillers, have shorter life spans, and though much improved over the years, are still more temperamental.

The refrigerants argument has been largely answered by the new generation of ozone-safe refrigerants. One should not forget that steam absorbers have a non-benign working fluid that can also leak and must be disposed of at the end of the product life cycle.

Absorbers have small legitimate niche applications. However, suggesting that they are a "proven workhorse technology" suitable for your average high school mechanical system deserves further clarification.

Editor's Note: John Kluber provided the following information in response to Alan Wright's letter.

To the Editor: From our experience, rotary screw water and centrifugal chillers cost $325 to $375 per ton. Air-cooled chillers have averaged between $425 and $450 per ton. For this project, the cost of the two absorbers was $246,200, which is $210 per actual operating tonnage of 585 tons per absorber. We recognize that equipment pricing is subject to many variables, but in this case they are nearly half the cost of air-cooled chillers.

Absorbers do require more heat rejection. The condenser pipes, pumping, and towers are larger when compared to electric water-cooled chillers, but not twice as large, as suggested. The absorbers required 2,000 tons of tower capacity with a pumping capacity of 3.4 gpm per ton based upon a 15-degree delta tee. If centrifugals were installed, the towers would have been 1,500 tons with a pumping flow rate of 2.5 gpm. The towers were located below the chillers to minimize piping. A 16-inch supply and return header was installed with two 30-hp condenser pumps for a brake horsepower of 25.3.

For centrifugal chillers, the system would have required 12-inch headers and 25-hp pumps for a brake horsepower of 22.9. Due to the proximity and cost of the towers, the initial cost was not significant.

Low-temperature air systems coupled with heat pipe heat recovery significantly reduced the initial costs. Also, when reducing leaving evaporative water temperatures, more energy is required and chillers must be derated.

The absorbers require more steam and electric chillers require larger compressors. Steam allowed for the production of low water temperature of 40 °F. Fabric ductwork works very well for low-temp systems and eliminates the issue of condensation.

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