Magentic Refrigeration

In 1881, the German physicist Emil Warburg put a block of iron into a strong magnetic field and found it increased very slightly in temperature. Scientists now know the electrons pivot in the field to align at a lower energy state, releasing surplus energy. The metal warms up in what's known as the magnetocaloric effect, which is greatest near the magnetic phase transition temperature.

"If you can suddenly alter the degree of ordering of all these little spins, then you get a large response," says Sandeman. For iron at room temperature, the response is just 0.1C. Some materials cool in a magnetic field, a property that's used in low temperature research. Finding the right room temperature material is the key to a magnetic fridge, where the cooling power is derived from a positive magnetocaloric effect coupled to heat exchange.

One material works nicely: the element gadolinium (Gd). It's a silvery-white metal that's strongly attracted by a magnet, has a magnetic disordering temperature of 20C, and a giant magnetocaloric effect of several degrees. A waste product from permanent magnet manufacture, gadolinium costs around £100 per kg; a magnetic fridge would use 0.15kg. Sandeman's current research, however, is looking at other possibilities.

For Next read.....http://www.e-refrigeration.com/index.php?page=magnetic-refrigeration

The Need for HVAC Schools and Training

The career opportunities in Heating, Ventilation, Air conditioning, and cooling systems (HVAC) are nearly limitless. A career in this field means that a person will be engaged in an industry revolution as equipment becomes more efficient and the industry adopts more energy saving procedures. Since HVAC equipment has become much more sophisticated; technology and skillful HVAC training is more critical today than ever. Nearly every enclosed space relies on some form of heating, ventilation, and air conditioning, or HVAC. This means there is a need for more technicians with better HVAC technical training.

An HVAC mechanic must be skilled in many aspects. Hospitals, schools, office buildings, malls, and apartment buildings have very complicated climate systems in place that can only be cared for by highly skilled and trained professionals. Typically, after graduating from a HVAC school, you can choose a job that focuses on HVAC system design, maintenance, and repair. There are other areas of expertise in HVAC training involving hydronics (water-based heating systems), solar panels, or commercial refrigeration.

During HVAC training, you'll also become familiar with reading and analyzing data from voltmeters, pressure gauges, manometers, and additional testing devices that monitor airflow, refrigerant pressure, electrical circuits, burners, and other components.

At The Refrigeration School, Inc (RSI), you will be taught to read blueprints; learn about safety issues, tools of the trade, designs, equipment construction, , and the installation, maintenance and repair of heating, ventilation, air conditioning and refrigeration systems.

While HVAC mechanics of years past might have learned on the job, as equipment becomes more efficient and the industry adopts more technologically advanced energy saving devices, most employers expect you to have completed formal HVAC training certifications. HVAC training has seen major changes over the past few years as a result of the national importance of energy conservation. The technicians who maintain and operate modern environmental systems are in huge demand in today's job market. Concerns about energy efficiency and new technologies have produced terrific opportunities for people with the right HVAC training. Job prospects for heating, air-conditioning, and refrigeration mechanics and installers are expected to be excellent, particularly for those with technical school or formal apprenticeship training. Employment of heating, air-conditioning, and refrigeration mechanics and installers is predicted to grow faster than the average for all occupations through the year 2012 according to the US Department of Labor. New concern for energy conservation should continue to rapidly develop new energy-saving heating and air-conditioning systems.

Basics For Absorption Chillers
By Vincent A.Sakraida, P.E.
If motor-driven vapor compression chillers are much more energy efficient than absorption chillers, then why are we even
having this conversation? In a hunt for LEED® points or in applications with certain demands, absorption could be just the
ticket to sustainability and/or economy.

Does the idea of using steam, hot water, or direct-fired burners to generate chilled water sound like an oxymoron? Well,
absorption chillers use these thermal energy sources to produce chilled water. Beyond the type of thermal energy source,
absorption chillers are also classified by whether they are single- or double-effect. The goal of this article is to
provide the reader with a basic description of absorption chillers and their advantages, specific applications,
performance standards, and energy efficiency, plus how they can be used to gain LEED® certification points.

Water As A Refrigerant

How about using water as a refrigerant and lithium bromide as a salt to absorb the water? These are certainly not easily
understood concepts. However, water has a very high specific heat and latent heat of vaporization, which makes it a great
refrigerant.

How is water boiling at 212°F going to create chilled water at 44°? First, the boiling temperature of water is a direct
function of pressure and at a pressure of 1 atmosphere (29.92 Hg), water boils at 212°. When the pressure on the water is
decreased, the water boiling temperature is lowered. The following table gives the total pressure in inches of mercury and
the corresponding approximate water boiling temperature at different pressures:

Absolute pressure Water boiling point (°F)
29.92 Hg (1 atm) 212°
2.99 Hg (0.1 atm) 115°
1.01 Hg 80°
0.30 Hg (0.01 atm) 45°
0.23 Hg 38°

Absorption chillers have substantially reduced internal pressures to take advantage of the lower water boiling
temperatures. Absorption chiller internal pressures can range from 0.1 atmosphere (atm) to below 0.01 atm.

Absorption Chiller Description

There are a number of absorption chillers available, including single-effect indirect-fired (steam, hot water);
double-effect indirect-fired; and double-effect direct-fired (gas and/or oil burner). Single-effect absorption chillers
have a single generator/concentra tor and condense all vaporized refrigerant in a single condenser. Double-effect
absorption chillers have two generator/concentra tors and the vaporized refrigerant from the high temperature
generator/concentra tor is the thermal source for the low temperature generator/concentra tor, reducing the cooling
requirement for the vaporized refrigerant.

Single-effect indirect-fired chillers are typically available in capacities between 100 and 1,350 tons with one
manufacturer providing a unit up to 2,000 tons. Double-effect indirect-fired chillers are typically available in
capacities between 100 and 1,500 tons, although one manufacturer provides a unit up to 5,000 tons. Double-effect
direct-fired chillers are typically provided in capacities between 100 and 1,500 tons.

A description of the various single-effect, indirect-fired absorption chiller components is provided below followed by a
description of the double-effect absorption chiller component that is different than the single-effect absorption chiller.

Single-effect absorption chiller. The single-effect indirect-fired absorption chiller has five main steps (Figure 1):
condensing (condenser), expansion (expansion pipe), evaporation (evaporator) , absorption (absorber), and
generator/concentra tor. See Figure A for schematic chiller diagram and Diagram 1 for the Duhring pressure/temperatur e
diagram. Like the vapor compression chillers, absorption chillers have a high-pressure side (generator/concentr ator,
condenser) and low-pressure side (expansion pipe, evaporator, absorber). The following component descriptions will include
some available options and standard operating parameters:
a.. Condenser. In the condenser, the cooling water absorbs the heat of condensation from the vaporized refrigerant,
changing the refrigerant into a liquid.

b.. Expansion. The liquid refrigerant (water) travels from the condenser (0.1 atm) through expansion piping to the
evaporator (less than 0.01 atm) during which the liquid refrigerant experiences a drop in pressure and temperature. The
liquid refrigerant is discharged into a pan within the evaporator.

c.. Evaporator. The liquid refrigerant (water) is pumped to the chilled water tube bundle top and sprayed on the tube
bundle. At the low evaporator pressure (less than 0.01 atm), the liquid refrigerant vaporizes at approximately 38°,
removing energy from the chilled water. Most lithium bromide absorption chillers can only produce chilled-water supply
temperatures down to 40°. Liquid refrigerant that is not vaporized drops down to the pan and is recirculated. Liquid
refrigerant that is vaporized travels from the evaporator to the absorber.

d.. Absorber. The vaporized refrigerant enters a liquid lithium-bromide solution spray within the absorber. The lithium
bromide solution absorbs the vaporized refrigerant and the cooling water absorbs the heat of vapor absorption. After the
absorption, the liquid lithium-bromide solution takes one of two paths. One path has the liquid bromide solution mixing
with a concentrated lithium bromide solution and being pumped to the absorber spray nozzles. The other path has the liquid
bromide solution being heated and pumped to the generator/concentra tor.

e.. Generator/concentra tor. The lithium-bromide solution enters the generator/concentra tor and is heated by steam or hot
water, raising the lithium bromide solution to a temperature where the liquid refrigerant (water) vaporizes and travels to
the condenser, completing the refrigerant cycle. The concentrated lithium bromide solution flows down to the absorber,
completing the absorber cycle.
f.. Double-effect absorption chiller. The double-effect chiller condensing (condenser), expansion (expansion pipe),
evaporation (evaporator) , and absorption (absorber) steps are the same as the single-effect chiller. The double-effect
chiller has an additional generator/concentra tor step that improves the overall efficiency of the chiller (Figure 2). The
following is a description of the double-effect chiller generator/concentra tion.

g.. Generator/concentra tor. The lithium-bromide solution enters the low-temperature generator/concentra tor and is heated
by the high temperature generator/concentra tor vaporized refrigerant, raising the lithium-bromide solution to a
temperature where the liquid refrigerant vaporizes and travels to the condenser. The high-temperature vaporized
refrigerant discharges into the condenser.

The concentrated lithium bromide solution takes one of two paths. One path has the lithium-bromide solution flowing down
to the absorber, being mixed with higher concentrated lithium-bromide solution coming from the high temperature
generator/concentra tor, heated, and discharged into absorber. The other path has the lithium-bromide solution being heated
and pumped to the high temperature generator/concentra tor where steam, hot water, or direct-fired heating is applied to
raise the lithium bromide solution to a temperature where the liquid refrigerant vaporizes and travels to the condenser.
The highly concentrated lithium bromide solution is mixed with the concentrated lithium bromide going to the absorber.

Chiller Performance Standard

The primary absorption chiller performance standard is ARI Standard 560 (2000 Standard for Absorption Water Chilling and
Water Heating Packages). ARI Standard 560 applies to water cooled single-effect steam chillers, water cooled single-effect
hot water chillers, water cooled double-effect steam chillers, water cooled double-effect hot water chillers, and water
cooled double-effect direct-fired chillers. This standard provides testing standard conditions, rating requirements,
minimum data requirements for published ratings, and integrated part load value (IPLV) or non-standard part load value
(NPLV).

For performing the IPLV testing, ARI Standard 560 has established standard conditions for absorption chillers including:
a.. Entering condenser water temperature: 85°
b.. Condenser water flow rate: 3.6 gpm/ton (single-effect indirect fired)
c.. 4.0 gpm/ton (double-effect indirect fired, double-effect direct-fired)
d.. Condenser water-side fouling factor: 0.00025
e.. Evaporator leaving water temperature: 44°
f.. Evaporator water flow rate: 2.4 gpm/ton
g.. Evaporator waterside fouling factor: 0.0001
h.. Tube-side fouling factor (steam): 0.000 (indirect fired)
i.. Tube-side fouling factor (hot water): 0.0001 (indirect fired)
It is very important to understand that chillers rarely operate at their maximum capacity. ARI used typical building types
and operations in 29 different cities to develop a chiller loading profile during a typical year. The resulting chiller
loading profile is at 100% capacity about 1% of the time, 75% capacity about 42% of the time, 50% capacity about 45% of
the time, and 25% capacity about 12% of the time. These values are incorporated into the IPLV equations, which are:

IPLV = 0.01A + 0.42B + 0.45C + 0.12D

(coefficient of performance [COP]) where:

A = COP at 100% capacity (condenser water at 85° )
B = COP at 75% capacity (condenser water at 77.5° )
C = COP at 50% capacity (condenser water at 70°)
D = COP at 25% capacity (condenser water at 70°)

IPLV = 1 (MBtuh/ton) where:
(0.01/A) + (0.42/B) + (0.45/C) + (0.12/D)

A = MBtuh/ton at 100% capacity (condenser water at 85° )
B = MBtuh/ton at 75% capacity (condenser water at 77.5°)
C = MBtuh/ton at 50% capacity (condenser water at 70°)
D = MBtuh/ton at 25% capacity (condenser water at 70°)

When evaluating different chiller energy usage, the IPLV provides the most accurate average chiller energy usage. When the
known parameters are different than prescribed above, the part-load performance becomes NPLV which has the same equation
as the IPLV. Ultimately, the chiller's energy usage is primarily based upon the "lift" or temperature difference between
the chilled water leaving temperature and condenser water leaving temperature. Lowering the condenser water leaving
temperature or raising the chilled water leaving temperature will reduce lift and energy usage of chiller, but not
necessarily chilled water system. Raising the condenser water leaving temperature or lowering the chilled water leaving
temperature will increase lift and energy usage of chiller.

Chiller Operating Performance

As with motor-driven vapor compression chillers, absorption chillers do not operate at the standard operating conditions
noted above. Though there are many variables that can be evaluated; for this article, absorption chiller COP vs.
part -load percentage and chilled water leaving temperature vs. chiller capacity shall be evaluated. Note that the graphs
are illustrative only. It is important that you use the particular chiller performance data for the equipment you are
evaluating.

Effect of part-load operation on chiller efficiency. Looking at Graph 1, all three types of absorption chillers are most
efficient at 50% part load with the single-effect indirect-fired chiller having a 9.4% increase in efficiency; the
double-effect direct-fired chiller having a 10% increase in efficiency; and the double-effect indirect-fired chiller
having a 16.7% increase in efficiency. At part loads below 50%, the chiller efficiencies are lower as the chiller part
load is lower.

Effect of chilled water leaving temperature. The standard chilled water leaving temperature is 44°. Looking at Graph 2,
chiller capacity increases as the chilled water leaving temperature increases. At a chilled water leaving temperature of
48°, the chiller capacity increased 8% for single-effect absorption chiller and increased 9.5% for double-effect
absorption chiller as compared to chilled water leaving temperature of 44°.

Conversely, the chiller capacity decreases as the chilled water leaving temperature decreases. At a chilled water leaving
temperature of 40°, the chiller capacity decreased 14.5% for single-effect chiller and decreased 11.4% for double-effect
absorption chiller as compared to chilled water leaving temperature of 44°.

Aborption Chillers And LEED®

The USGBC LEED for New Construction, Version 2.2, has a mandatory prerequisite to reduce ozone depletion by utilizing no
CFC refrigerants in new construction and phasing out CFC refrigerants during renovation of existing facilities. Since the
two frequently used absorption chiller refrigerants are ammonia and water, absorption chillers meet the Energy &
Atmosphere Prerequisite 3, Fundamental Refrigerant Management, requirement of no CFC refrigerants.

The USGBC also provides the opportunity for obtaining a credit for Enhanced Refrigerant Management. Understanding some
lower ozone-depleting refrigerants are also less efficient, the Energy & Atmosphere Credit 4, Enhanced Refrigerant
Management has developed a formula that weighs a refrigerant' s ozone depletion and global warming potentials. If the
project's total installed refrigerant has an average atmospheric impact less than a 100, it is eligible for the credit
(See USGBC for further information on formula).

The credit also recognizes "natural refrigerants" like water, carbon dioxide, ammonia, and propane as having a lower
atmospheric damage potential and will allow projects exclusively using natural refrigerants to claim the credit without
using the Enhanced Refrigerant Management formula. Absorption chillers can be a key component in meeting the USGBC
strategy of reducing atmospheric damage.

Absorption Chiller Energy Efficiency

Absorption chiller energy efficiency is based upon fuel consumption per ton cooling while motor driven vapor compression
chiller energy efficiency is based upon kW/ton cooling. The COP is a method for determining overall chiller energy
performance.

For absorption chillers, the COP formula is:

COP = Eu / Ea

where: Eu = useful energy obtained (Btuh)

Ea = energy used (Btuh)

For motor-driven chillers, the COP formula is:

COP = 12
KW/ton x 3.412

Per manufacturer supplied information, the coefficient of performance range for the different absorption chiller types are
as follows:

Absorption chiller type COP range

Hot water or steam
single-effect chiller..... ......... 0.60 to 0.75

Hot water or steam
double-effect chiller..... ........1. 19 to 1.35

Direct fired double-effect
chiller..... ......... ......... ......... .......1. 07 to 1.18

Looking at the COP ranges, the single-effect chiller is the least energy-efficient absorption chiller type with the hot
water, steam, and direct-fired, double-effect absorption chillers being almost twice as energy efficient. The hot water
and steam double-effect absorption chillers are the most energy efficient absorption chillers, but how do they compare to
motor driven vapor compression chillers?

The two motor-driven vapor compression chillers being utilized for energy efficiency comparison are the water cooled
rotary screw chiller and the water cooled centrifugal chiller. Per manufacturer supplied information, the water cooled
rotary screw chiller has a COP range of 3.90 to 5.40 while the water cooled centrifugal chiller has a COP range of 7.00 to
8.79. The result is that motor driven vapor compression chillers are 4 to 7 times more energy efficient than absorption
chillers. This leads to a question: Why would you want to use an absorption chiller?

Advantages Of Using Absorption Chillers

In an energy-efficiency competition, motor-driven vapor compression chillers will beat absorption chillers every time.
However, there are specific applications where absorption chillers have a substantial advantage over motor-driven vapor
compression chillers. Some of those applications include:
a.. For a facility that has a cogeneration power plant or other thermal energy generating process with excess thermal
energy, absorption chillers can utilize this excess thermal energy to produce chilled water instead of all the excess
thermal energy being wasted.
b.. For a facility that has inadequate electrical infrastructure or bringing electrical infrastructure to the facility
is cost prohibitive, absorption chillers have a substantially lower electrical power requirement than motor driven vapor
compression chillers.
c.. For a facility with high electrical power cost and low fuel cost, absorption chillers may have a lower operating
cost than motor driven vapor compression chillers.
d.. For a facility that requires substantial system reliability, the lower electrical requirements for absorption
chillers will reduce emergency generator load requirements.
e.. For a facility that has high electrical demand charges, absorption chillers can be used as part of a peak shaving
strategy.
f.. For a facility that has very low acoustical and/or vibration requirements, absorption chillers have lower noise and
vibration generation than motor driven vapor compression chillers.
g.. For a facility wanting to use a "natural refrigerant, " absorption chillers are a good choice.

Summary

The future for absorption chillers is bright. With power utilities increasing electrical demand charges during peak hours
as a strategy to delay building new power generating stations, absorption chillers can be the corner stone for an
electrical demand limit strategy. With absorption chillers using "natural refrigerants, " they will become more attractive
as more restrictions are placed on HCFC and other refrigerants. With the improved lithium bromide solution concentration
control, absorption chillers are more reliable. ES

Refrigeration

Design untuk Sistem Absorption Chiller
Secara garis besar, langkah2 Desainnya kurang lebih begini (Hanya dengan melakukan perhitungan kesetimbangan massa dan heat) :

1. Kita tetapkan peruntukan Absorption Chiller ( Temperatur beban dan kapasitas pendingin)

2. Tentukan type Absorption chiller (LiBr-Water/ Ammonia-Water, dengan sistem Dobble effect/single effect, ataupun dengan heat source apa : direct fire, steam or Hot water ?)
3.Dari kapasitas pendingin dan temperatur, kita bisa dapatkan flow refrigerant dan desain HE evaporator.

4. Dari sini dapatkan desain ABsorber dengan (mis. LiBr-WAter), kita akan dapatkan jumlah absorber yang diperlukan (Dari kapasitas daya serap LiBr, lewat tabel Duhring).

5. Menentukan design Generator (Tentukan heat pada tekanan kerja untuk menghasilkan jumlah penguapan/flow refrigeran yg diperlukan)

6. Berikutnya design kondensor dengan tentunya mengetahui media pendinginannya atau temperatur kondensasinya.

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