Nanoscience is the study of molecules and molecular structures, called nanostructures, having one or more dimensions less than about 100 nanometers. One nanometer is one-billionth of a meter: 1 nm = 10-9 m. To grasp this level of smallness, a stack of 10 hydrogen atoms would have a height of 1 nm, while a human hair has a diameter of about 50,000 nm. Nanotechnology is the engineering of nanostructures into useful products. At the nanotechnology scale, behavior may differ from our macroscopic expectations. For example, the averaging used to assign property values at a point in the continuum model may no longer apply owing to the interactions among the atoms under consideration. Also, at these scales, the nature of physical phenomena such as current flow may depend explicitly on the physical size of devices. After many years of fruitful research, nanotechnology is now poised to provide new products with a broad range of uses, including implantable chemotherapy devices, biosensors for glucose detection in diabetics, novel electronic devices, new energy conversion technologies, and smart materials as, for example, fabrics that allow water vapor to escape while keeping liquid water out.
Nanoscale Machines on the Move
Engineers working in the field of nanotechnology, the engineering of molecular-sized devices, look forward to the time when practical nanoscale machines can be fabricated that are capable of movement, sensing and responding to stimuli such as light and sound, delivering medication within the body, performing computations, and numerous other functions that promote human well-being. For inspiration, engineers study biological nanoscale machines in living things that perform functions such as creating and repairing cells, circulating oxygen, and digesting food. These studies have yielded positive results. Molecules mimicking the function of mechanical devices have been fabricated, including gears, rotors, ratchets, brakes, switches, and abacus-like structures. A particular success is the development of molecular motors that convert light to rotary or linear motion. According to researchers, Although devices produced thus far are rudimentary, they do demonstrate the feasibility of constructing nanomachines.
Fig. Molecular Motor
Drafting occurs when two or more moving vehicles or individuals align closely to reduce the overall effect of drag. Drafting is seen in competitive events such as auto racing, bicycle racing, speed-skating, and running.
Studies show that air flow over a single vehicle or individual in motion is characterized by a high-pressure region in front and a low-pressure region behind. The difference between these pressures creates a force, called drag, impeding motion. During drafting, as seen in the sketch below, a second vehicle or individual is closely aligned with another, and air flows over the pair nearly as if they were a single entity, thereby altering the pressure between them and reducing the drag each experiences. While race-car drivers use drafting to increase speed, non–motor sport competitors usually aim to reduce demands on their bodies while maintaining the same speed.
The energy required by animals to sustain life is derived from oxidation of ingested food. We often speak of food being burned in the body. This is an appropriate expression because experiments show that when food is burned with oxygen, approximately the same energy is released as when the food is oxidized in the body. Such an experimental device is the well-insulated, constant-volume calorimeter shown in Fig. below.
A carefully weighed food sample is placed in the chamber of the calorimeter together with oxygen (O2). The entire chamber is submerged in the calorimeter’s water bath. The chamber contents are then electrically ignited, fully oxidizing the food sample. The energy released during the reaction within the chamber results in an increase in calorimeter temperature. Using the measured temperature rise, the energy released can be calculated from an energy balance for the calorimeter as the system. This is reported as the calorie value of the food sample, usually in terms of kilo-calorie (kcal), which is the “Calorie” seen on food labels.
All activities in nature involve some interaction between energy and matter; thus it is hard to imagine an area that does not relate to thermal‑fluid sciences in some manner. Therefore, developing a good understanding of basic principles of thermal‑fluid sciences has long been an essential part of engineering education.
Thermal‑fluid sciences are commonly encountered in many engineering systems and other aspects of life, and one does not need to go very far to see some application areas of them. In fact, one does not need to go anywhere. The heart is constantly pumping blood to all parts of the human body, various energy conversions occur in trillions of body cells, and the body heat generated is constantly rejected to the environment. Human comfort is closely tied to the rate of this metabolic heat rejection. We try to control this heat transfer rate by adjusting our clothing to the environmental conditions. Also, any defect in the heart and the circulatory system is a major cause for alarm.
Other applications of thermal‑fluid sciences are right where one lives. An ordinary house is, in some respects, an exhibition hall filled with wonders of thermal‑fluid sciences. Many ordinary household utensils and appliances are designed, in whole or in part, by using the principles of thermal‑fluid sciences. Some examples include the electric or gas range, heating and air‑conditioning systems, refrigerator, humidifier, pressure cooker, water heater, shower, iron, plumbing and sprinkling systems, and even the computer, TV, and DVD player.
Large scale applications
On a larger scale, thermal‑fluid sciences play a major part in the design and analysis of automotive engines, rockets, jet engines, and conventional or nuclear power plants, solar collectors, the transportation of water, crude oil, and natural gas, the water distribution systems in cities, and the design of vehicles from ordinary cars to airplanes (Fig. 1–2). The energy‑efficient home that you may be living in, for example, is designed on the basis of minimizing heat loss in winter and heat gain in summer. The size, location, and the power input of the fan of your computer is also selected after a thermodynamic, heat transfer, and fluid flow analysis of the computer.
- Fundamentals of Thermal-Fluid Sciences by Yunus A. Cengel
How does an Electric car work – No Carbon dioxide emission
From outside most electric cars look exactly like fossil fuel-powered cars. An electric car lacks a tailpipe and gas tank, but the overall structure is basically the same. Under the bonnet, instead of a huge engine all you will see is an electric motor and its controller. The electric motor needs no oil, no tune-ups, and since there is no tailpipe emissions, it does not necessitate any smog checks.
The electric vehicle power source is the battery which acts as a “gas tank” and supplies the electric motor with the energy necessary to move the vehicle. This gives the car acceleration. When the vehicle is idle there is no electrical current being processed, so energy is not being used up. The controller acts as a regulator, and controls the amount of power received from the batteries so the motor does not burn out. This battery powers all of the electronic devices in the car, just like the battery in a gas-powered car. Everything else in the electric car is basically the same as its gas-powered equivalent: transmission, brakes, air conditioning, and airbags. Since electric vehicles use an electric motor, the driver can take advantage of the motor’s momentum when pressure is applied on the brakes. Instead of converting all the potential energy in the motor into heat like a fossil fuel-powered car does, an electric car uses the forward momentum of the motor to recharge the battery. This process is called regenerative braking.
Advantages of an Electric car
There are many environmental benefits and personal benefits for having an electric car:
- Most electric motors can travel up to 150 – 180 km before they need to be charged
- No tail pipe exhaust means no greenhouse gases such as CO2, NOx and PM10s
- No oil consumption means less reliance on fuel
- Cars can be recharged whenever is convenient to the user
- More cost-effective than regular cars because of long-lasting battery use
- Cheaper to maintain because they have fewer moving parts
- Creates less noise pollution because the engine is silent