Heat Pumps

Heat Pumps is the topic of our upcoming meeting on Thursday March 27 at CIT (see previous article). Just in case you need to brush up on the basic operating principals check out the Wikipedia article on heat pumps. I've enclosed some of it here for you all to read. See you all at the meeting.

Operation
Main article: Heat pump and refrigeration cycle
According to the second law of thermodynamics heat cannot spontaneously flow from a colder location to a hotter area; work is required to achieve this.[2] Heat pumps differ in how they apply this work to move heat, but they can essentially be thought of as heat engines operating in reverse. A heat engine allows energy to flow from a hot 'source' to a cold heat 'sink', extracting a fraction of it as work in the process. Conversely, a heat pump requires work to move thermal energy from a cold source to a warmer heat sink.
Since the heat pump uses a certain amount of work to move the heat, the amount of energy deposited at the hot side is greater than the energy taken from the cold side by an amount equal to the work required. Conversely, for a heat engine, the amount of energy taken from the hot side is greater than the amount of energy deposited in the cold heat sink since some of the heat has been converted to work.
One common type of heat pump works by exploiting the physical properties of an evaporating and condensing fluid known as a refrigerant.

A simple stylized diagram of a heat pump's vapor-compression refrigeration cycle: 1) condenser, 2) expansion valve, 3) evaporator, 4) compressor.
The working fluid, in its gaseous state, is pressurized and circulated through the system by a compressor. On the discharge side of the compressor, the now hot and highly pressurized gas is cooled in a heat exchanger called a condenser until it condenses into a high pressure, moderate temperature liquid. The condensed refrigerant then passes through a pressure-lowering device like an expansion valve, capillary tube, or possibly a work-extracting device such as a turbine. This device then passes the low pressure, barely liquid (saturated vapor) refrigerant to another heat exchanger, the evaporator where the refrigerant evaporates into a gas via heat absorption. The refrigerant then returns to the compressor and the cycle is repeated.
In such a system it is essential that the refrigerant reaches a sufficiently high temperature when compressed, since the second law of thermodynamics prevents heat from flowing from a cold fluid to a hot heat sink. Similarly, the fluid must reach a sufficiently low temperature when allowed to expand, or heat cannot flow from the cold region into the fluid. In particular, the pressure difference must be great enough for the fluid to condense at the hot side and still evaporate in the lower pressure region at the cold side. The greater the temperature difference, the greater the required pressure difference, and consequently more energy is needed to compress the fluid. Thus as with all heat pumps, the energy efficiency (amount of heat moved per unit of input work required) decreases with increasing temperature difference.
Due to the variations required in temperatures and pressures, many different refrigerants are available. Refrigerators, air conditioners, and some heating systems are common applications that use this technology.
In HVAC applications, a heat pump normally refers to a vapor-compression refrigeration device that includes a reversing valve and optimized heat exchangers so that the direction of heat flow may be reversed. The reversing valve switches the direction of refrigerant through the cycle and therefore the heat pump may deliver either heating or cooling to a building. In the cooler climates the default setting of the reversing valve is heating. The default setting in warmer climates is cooling. Because the two heat exchangers, the condenser and evaporator, must swap functions, they are optimized to perform adequately in both modes. As such, the efficiency of a reversible heat pump is typically slightly less than two separately-optimized machines.
In plumbing applications, a heat pump is sometimes used to heat or preheat water for swimming pools or domestic water heaters.
In somewhat rare applications, both the heat extraction and addition capabilities of a single heat pump can be useful, and typically results in very effective use of the input energy. For example, when an air cooling need can be matched to a water heating load, a single heat pump can serve two useful purposes. Unfortunately, these situations are rare because the demand profiles for heating and cooling are often significantly different.

Monthly Meeting

The monthly meeting for LVRSES will be held on Thursday March 27, 6-8PM at CIT ( Career Institute of Technology) in Forks twsp. http://www.citvt.com/

Our speaker will be Mr. Kevin Wasieleski CM and the topic will be Heat Pumps. Kevin has recently completed a book on this subject and has agreed to share his expertise in this area. You don't want to miss this educational session. We will have a short business meeting after the educational session. Refreshments will be served.

Directions to CIT: From route 22 take route 33N to the Stockertown/191 exit. Turn right at the end of ramp and follow route 191 a short distance to Main St./Sullivan Trail in Stockertown. Turn right and follow for 1 1/2 miles to traffic light at Uhler Rd. Turn left onto Uhler Rd. and follow for 1 mile to traffic light at Kesslersville Rd. Turn left onto Kesslersville Rd.. CIT is 1 mile on the right. The meeting will be held in the Industrial Conference room. Look for RSES signs.

HVAC filters

I came across an interesting article about HVAC filtration. In the interest of posting more articles on the blogsite, I thouht it would be good to share with all of you. Mike

HVAC FILTERS: Energy Savings 101: Cutting Energy Costs While Improving IAQ
According to the U.S. Department of Energy, our nation’s K-12 schools spend $6 billion on energy, while colleges and universities spend close to $2 billion each year. Healthcare facilities also spend a staggering amount on energy—$5.3 billion annually.
Switching to a lower pressure drop filter is one of the easiest changes for facility managers to make in an effort to reduce energy costs.
In many cases, older buildings, with their aging mechanical systems, are to blame for energy inefficiencies. In fact, a significant portion of energy costs for educational and healthcare facilities can be tied to space heating and cooling, thanks in part to HVAC systems that are not optimized for energy conservation.Improving an HVAC system’s energy efficiency does not have to be daunting or costly, however. For example, simply upgrading the HVAC air filtration system can help to reduce energy costs while also improving indoor air quality (IAQ)–an issue of increasing importance in terms of its effect on academic performance and patient comfort.Using Filters to Conserve EnergyHVAC filters play a key role in the HVAC system: they remove contaminants from the air that passes through the system, and they protect HVAC equipment from dust that can increase operating costs. Filters also play a role in the energy consumed to operate the system. The energy used is based on the resistance of the air passing through the filter: the lower the filter’s resistance, the lower the energy consumption will be. However, even though one speaks of filters, it is really the filter media that has the biggest effect on minimizing energy consumption, protecting HVAC equipment and providing clean air. Unfortunately, many filter suppliers consider the media used in the filters as a commodity, resulting in the filter’s price being the determining selection factor. It is important to understand though that the cost of energy used by filters far outweighs the initial price of the filter itself. In fact, energy costs can be 10 times the initial filter price for a standard pleated filter and 4-5 times the initial filter cost for higher efficiency final filters. The good news is that more energy-efficient filters do not necessarily need to cost more, so energy savings can often be achieved without any investment, thanks to recent advances in filtration media technology.Lifecycle CostsThe best way to use filters as an energy conservation tool is to consider the total life-cycle cost of the filter and the filter’s long-term effect on energy costs. The three major components of life-cycle cost for HVAC filters are: initial price and maintenance, energy consumption and disposal. On average, energy cost accounts for an astounding 81 percent of the total life-cycle cost of a filter system. The initial price and maintenance accounts for 18 percent and disposal accounts for 1 percent.How can life-cycle costs of filters be applied to energy efficiency? The key issue is the filter’s pressure drop, as measured by two filter test standards from the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE): ASHRAE 52.1-1992 and ASHRAE 52.2-1999. Development of new materials has given the filter industry a chance to produce lower pressure-drop media while maintaining high particle capture efficiencies, thereby providing the ability to reduce electricity costs and improve IAQ simultaneously. Electret technology and electrostatic filter media have been the key technologies enabling this seemingly contradictory concept to become a reality. In fact, today, there are 95 percent efficiency synthetic media filters that have the same pressure drop as 65 percent efficiency glass media filters, providing the ability to increase filtration efficiency in commercial/institutional HVAC systems by 30 percent without increasing energy costs at all. Switching to a lower pressure drop filter is one of the easiest changes for facility managers to make in an effort to reduce energy costs. That is because, with a lower pressure drop filter, the HVAC system motor needs to overcome less resistance to deliver the required air flow, thus reducing the motor’s energy consumption.
The following figures illustrate the impact of a filter’s pressure drop on annual energy costs. Note that the two commercially available filters are identical except for the initial pressure drop. In a typical scenario, one might use initial price as the primary criteria in choosing one of these filters over the other. However, as the example shows, this might not result in the correct filter choice for maximizing long-term cost savings. In this example, initial price is the same to illustrate the effect of pressure drop on operating costs.Filter A provides a lower initial and average pressure drop and therefore saves approximately $29 in energy costs annually. While an energy

Filter A
Filter B
Efficiency
MERV 14
MERV 14
Filter Style
12” Deep Rigid
12” Deep Rigid
Media Area
120 sq. ft.
120 sq. ft.
Cost
$70
$70
Initial ΔP
0.45” WG
0.65” WG
Final ΔP
1.50” WG
1.50” WG
DHC
300 g
300 g
Filter Life
12 months
12 months
Energy Cost
$276/year
$305/year

Calculation:Energy Consumption = Q*dP*t/n/1000Assumes 24/7/365 operation, energy cost of$0.08/kWh, fan, motor, drive efficiency (n) of 58%WG = Water Gauge
savings of $29 per year may not sound like a lot, keep in mind that those cost savings are per filter, not for an entire HVAC system. Another way to look at the information is to consider that $29 saved with Filter A offsets 41 percent of the initial filter price. That is equivalent to nearly getting half of your filters free each year.
Installation and Maintenance IssuesOnce you have decided to upgrade your HVAC filter media to a lower pressure drop filter in an effort to reduce energy costs, it is time to swap out the old filters for new ones. The goal of proper filter installation is to avoid bypass air, which causes contamination in housings, coils, fans and ducts, and thus increases HVAC system operating costs. Do this by making sure all the air in the system goes through the filter. To avoid problems later on, consider these installation recommendations:• Make sure the replacement filters are of the correct size and compatible with your housing.• Check for filter media damage such as rips or holes, and discard damaged filters.• Make sure media is sealed in the frame to avoid bypass air.• Install the filter according to the air flow direction indicated on the frame. (Some filter manufacturers use a two-color filter media construction to help see which side faces upstream and which faces downstream.)• Ensure that the filter fasteners are in place and correctly installed, especially if filters are serviced from the down-streamside.• Check to ensure that the bank of filter frames is rigid and well reinforced to avoid collapse.• Caulk any cracks between filter frames or between the bank of frames and the duct wall to prevent leaking of unfiltered air.• Pay special attention to filter holding frame seals, gaskets and filters that do not match the filter holding frame size–all of which can cause bypass air.• Install a differential pressure measurement device across the filter bank to identify the appropriate change-out times. • Place labels on the housing units with information such as the number and type of filters, date installed and pressure drop to make changing filters easier.When inspecting filters, do not rely on a visual inspection for determining when to change filters. A dirty filter does not necessarily signify the end of a filter’s useful life. In addition, normal eyesight can only see particles of about 40 microns in size. Therefore, a filter rated at 10 microns can look dirty, yet still have an extensive useful service life. To extend the life-cycle of the filter, and reduce life-cycle costs, rely on the manufacturer’s suggested change-out frequency, or monitor the pressure drop of the filter and change the filter when it achieves its recommended final pressure drop.It is important to remember that better filtration does not always result in higher total costs. That is why facility managers considering the energy cost implications of a filter upgrade should ask their filter suppliers the following questions:• What pressure drop reduction offsets the difference in filter price?• At what pressure drop would a filter upgrade pay for itself?• At a given performance level, how much money could be saved by using a lower pressure drop filter?• How much of my filter costs does that cost savings offset?For an energy cost calculator to help determine the economic impact of various equally performing filters, visit http://www.kcfiltration.com/.Dave Matela, CAFSKimberly-Clark Filtration Products
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