HCMC UNIVERSITY OF TECHNOLOGY AND
EDUCATION
FACULTY FOR HIGH QUALITY TRAINING

PROJECT
Topic: Calculation and design pineapple
heat pump drying system
Course: Refrigeration Technology Projects
Instructor: Ph. D Le Minh Nhut
Student: Pham Van Long - 18147024

Ho Chi Minh city June, 2021


Feedback:

.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................

.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
Ho Chi Minh city, …/…/2021
Instructor’s signature


Acknowledgement
I have taken efforts in this project. However, it would not have been
possible without the kind support and help of many individuals and
organizations. I would like to extend my sincere thanks to all of them.
I am highly indebted to Ph.D Le Minh Nhut for their guidance and constant
supervision as well as for providing necessary information regarding the
project & also for their support in completing the project.
I would like to express my gratitude towards my all friends and lectures for
their kind co-operation and encouragement which help me in completion of this
project.
I would like to express my special gratitude and thanks to industry persons
for giving me such attention and time.
My thanks and appreciations also go to my colleague in developing the
project and people who have willingly helped me out with their abilities.

Ho Chi Minh City, June 2021
Student implementation:


Phạm Văn Long

1


Outline
ACKNOWLEDGEMENT…………………….………………………….1
LIST OF FIGURES……………………………….……………………...4
LIST OF TABLES……………………………….………………………5
SYMBOLS AND ABBREVIATIONS……………………………...…...6
Chapter 1: OVERVIEW………………………………………………….7
1.1. Reasons to choose the topic………………………………………..7
1.2. The purposes of the topic…………………………………………..8
1.3. The overview of the pineapple…………………………………….9
Chapter 2: BASIC THEORETICAL ……………………………….…..13
2.1. General about drying technology………………………………...13
2.1.1. Drying process………………………………………………...13
2.1.2. Drying methods classified…………………………………….13
2.1.3. Drying agent…………………………………………………..16
2.1.4. Drying mode…………………………………………………..16
2.2. General about Heat pump-drying………………………………...16
2.2.1. Principle diagram of Heat pump-drying………………………17
2.2.2. Coefficient of Heat pump-drying……………………………..19
2.2.3. Basic ingredients of Heat pump-drying……………………….20
Chapter 3: CALCULATION AND DESIGN…………………………...22
3.1. Design plans……………………………….……………………..22
3.1.1. Initial figures………………………….………………………22
3.1.2. Size of drying chamber……………………………………….22
3.2. Theoretical and practical drying process……….………………...22
3.2.1. Represent the theoretical drying process on the I-d graph……22

3.2.2. Represent the practical drying process on the I-d graph……...28
3.3. Parameters of the process………………………………………...38

2


3.4. Establishment of cycle calculation diagram………….…………..39
3.5. Compressor calculation………………………………………......41
3.6. Calculate resistance and fan……………………………………...43
3.7. Select the condenser………………………………………….….48
Chapter 4. ACTUAL EXPERIMENTAL SYSTEM……………………49
4.1. Heat pump system……………………………………………….49
4.2. Machine manufacturing results………………………………….51
4.3. The process of drying pineapple…………………………………52
Chapter 5: CONCLUSION AND RECOMMENDATION…………….55
5.1. Conclusion………………………………………………………..55
5.2. Recommendation…………………….…………………………...55
REFERENCES………………...………………………………………..56

3


LIST OF FIGURES
Figure 1.1 A pineapple on its parent plant………………………………………..10
Figure 2.1 Equipment’s diagram………………………………………………..….18
Figure 3.1 I-d graph represents the theoretical drying process………………..23
Figure 3.2 Heat of actual drying……………………………………………………29
Figure 3.3 Structure of drying chamber…………………………………………...31
Figure 3.4 I-d graph showing the actual drying process…………………….….35
Figure 3.5 Thermodynamic cycle of the compressor………………………….…39

Figure 4.1 4NES-20Y 4NCS-20.2Y Bitzer piston compressor 20HP………....49
Figure 4.2 Condenser and evaporator……………………………….………...….50
Figure 4.3 Principal diagram of heat pump……………………………………...50
Figure 4.4 Pineapple prepared…………………………………………………..…52
Figure 4.5 Pineapple are arranged on trays…………………………………..….53
Figure 4.6: Electrical cabinets……………………………………………………..54

4


LIST OF TABLES

Table 1. Nutrients in 100 grams(g) Pineapple……………………………….…...10
Table 3.1: state parameters at nodes……………………………………………….27
Table 3.2: Status parameter table at the actual drying process nodes……...…37
Table 3.3: Table of status parameters at nodes……………………………...…...40
Table 3.4: Indoor unit parameters………………………………………………….44
Table 3.5: Parameters of Condenser……………………………………………….46
Table 4.1: Technical parameters of heat pump dryer……………………………51

5


SYMBOLS AND ABBREVIATIONS
V

Volume, [m3]

G


Weight, [kg]

φ

Humidity, [%]

p

Specific weight, [kg/m3]

t

Temperature, [oC]

d

Vapor moisture content, [kg moisture/ kg kk]

h

enthalpy, [kJ/kg kk]

λ

Heat conductivity coefficient, [W/m.K]

δ

Thickness, [m]


α

Heat release coefficient, [W/m2.K]

ν

Velocity of drying agent, [m/s]

cp

Specific heat, [kJ/kg.K]

k

Heat transfer coefficient, [W/m2.K]

6


Chapter 1: OVERVIEW
1.1. Reasons to choose the topic.
A. Raw material drying.
Pineapple is a very delicious fruit and has a cooling effect in the
summer, in addition it is also processed into dried food. In 100g of the edible
pineapple contains 91.5g of water. The other ingredients are 6.5g glaucid;
15mg calcium mineral salts; 17mg phosphorus; iron 0.5mg; vitamin B1
0.08mg; beta-carotene 40mcg ... The pineapple nutrition in 100g provides
40kcal for the body. The enzyme bromelain contained in the pineapple
nutrition stimulates better digestion. Bromelain neutralizes body fluids so
that they do not become too acidic. So when we eat pineapple, we will

reduce heartburn. According to scientists also thanks to this substance,
pineapple is also very good for the functioning of the pancreas. According to
research, the vitamin C content in pineapples provides 50% of the
recommended daily amount of vitamin C. So that pineapple has the effect of
increasing the body's resistance. It helps to prevent damage to cells, prevents
some colds, flu, fever. Pineapple contains many essential minerals: calcium,
potassium, fiber, manganese, iodine ... In which, manganese is very good for
bones and connective tissue. With a glass of pineapple juice contains 73%
manganese content. According to a study in the US, manganese is very
helpful in preventing osteoporosis in postmenopausal women.

B. Heat Pump Drying technology.
Recently, it has been discovered that heat pump drying is an efficient
method of drying for drying industries. Heat pumps deliver more heat during
the drying process than the work input to the compressor. Heat pump drying
is a more advanced method than the traditional Viet Nam industrial and

7


agricultural drying methods, such as direct/indirect sunlight, wood
burning, fossil fuel burning, electrical heating and diesel engine heating.
Heat pump dryers provide high energy efficiency with controllable
temperature, air flow and air humidity and have significant energy-saving
potential. In the last decade the market for heat pump systems for water
heating and space cooling/heating has grown in Viet Nam, but the
development of heat pumps for industrial and agricultural drying is very
slow. The development of heat pump drying systems in Viet Nam is an
efficient way to solve energy problems in drying applications as this
technology is still in its infancy.

Thus, the discovery and widespread development of dehumidification
and cold drying systems for food, post-harvest agricultural products, forest
products and medicinal materials is an urgent requirement to encourage
agricultural development and structural transformation. crops, production of
alternative goods imported and exported to the world market, saving energy,
reducing investment capital and product costs.
Given the assignment of the topic as well as seeing the economic
benefits of pineapple and the practical effects that heat pump drying
technology brings in life, I would like to implement the topic "Design and
manufacture of systems. Pineapple heat pump drying ".
1.2. The purposes of the topic.
- Learn about heat pump drying technology, drying method and equipment in
heat pump drying system.
- Calculate and design pineapple heat pump drying system with a capacity of
200kg / batch.
- Fabrication of the heat pump drying system with calculated parameters.
- Testing and verifying the drying system on a real model.

8


1.3. Overview of the pineapple.
A. Appellation.
The pineapple (Ananas comosus) is a tropical plant with an edible fruit
and the most economically significant plant in the family Bromeliaceous. The
pineapple is indigenous to South America, where it has been cultivated for
many centuries. The introduction of the pineapple to Europe in the 17th
century made it a significant cultural icon of luxury. Since the 1820s,
pineapple has been commercially grown in greenhouses and many tropical
plantations. Further, it is the third most important tropical fruit in world

production. In the 20th century, Hawaii was a dominant producer of
pineapples, especially for the US; however, by 2016, Costa Rica, Brazil, and
the Philippines accounted for nearly one-third of the world's production of
pineapples.
B. Description.
The pineapple is a herbaceous perennial, which grows to 1.0 to 1.5 m (3 ft
3 in to 4 ft 11 in) tall, although sometimes it can be taller. In appearance, the
plant has a short, stocky stem with tough, waxy leaves. When creating its fruit,
it usually produces up to 200 flowers, although some large-fruited cultivars
can exceed this. Once it flowers, the individual fruits of the flowers join
together to create a multiple fruit. After the first fruit is produced, side shoots
(called 'suckers' by commercial growers) are produced in the leaf axils of the
main stem. These may be removed for propagation, or left to produce
additional fruits on the original plant.

9


Figure 1.1 A pineapple on its parent plant

C. Nutritional value.
Table 1. Nutrients in 100 grams(g) Pineapple
Nutrients

Amount

Energy

52 calories


Dietary fible

1.40 g

Carbohydrate

13.7 g

Protein

0.54 g

Iron

0.28 mg

Magnesium

12 mg

Calcium

16 mg

Potassium

150 mg

Phosphorus


11 mg

Zinc

0.10 mg

Vitamin A

130 I.U

Vitamin B1

0.079 mg

Vitamin B2

0.031 mg

10


Vitamin B3

0.489 mg

Vitamin B6

0.110 mg

Vitamin C


24 mg

D. Location and classified
Pineapples originated from the West Indies, Central America ... are
now cultivated in tropical climates such as the Philippines, Sumatra, Hawaii,
Sri Lanka, South America, Africa ... In Vietnam Pineapple is the key fruit in
processing to export. However, the output is very small compared to other
countries in the region. Pineapples are grown mainly in the Red River Delta
and the Mekong River Delta. There are many varieties of Pineapples,
classified into three main groups:
- Queen group: Pineapples belong to this group with medium weight and
magnitude, convex eyes, bear to transport, strong yellow flesh, strong aroma,
sweet taste. This is the group of Pineapples with the highest quality, which is
popularly grown in our country and is also known as Flower pineapple.
- The Cayenne group. This type has a large volume of fruit, sometimes up
to 3 kg. pulp is ivory-yellow, more watery, less fragrant and less sweet than
Flower pineapple. This variety is grown in many Pacific countries. This type,
though not very high quality, is grown a lot for processing because the large
fruit is easy to mechanize, giving high economic efficiency. Currently,
Vietnam is having a policy to develop this Pineapple variety.
- Spanish group (Spain). This pineapple has a larger fruit size than the
Flowering Pineapple, but smaller than the Cayenne Pineapple. The flesh is
light yellow to white, less fragrant, sour, more watery than Flower Pineapple.
Pineapples grown in Vietnam belong to this group. In addition to the three
main groups of Pineapples above, there is also the group Xan Miguel with
delicious yellow fruit.
E. Some study about pineapple.

11



Pineapples are a useful source of vitamins. A cup of pineapple chunks can
contain up to 28 milligrams of vitamin C, which is 382 Pineapple 31% of the
recommended daily vitamin C intake for men and 38% for women. The
water-soluble antioxidant properties of vitamin C help prevent scurvy,
increase immunity, and build resistance against infectious disease. Vitamin C
is a useful free radical scavenger and helps remove harmful free radicals from
the body. Vitamin C is also needed for the production of collagen, which is
the major structural protein required in the human body for maintaining the
integrity of blood vessels, skin, organs, and bones. Vitamin C present in
pineapples also contributes to oral health and helps with the prevention of
gum disease. Vitamin C reduces the risk of colon, esophagus, and stomach
cancer. Vitamin A and beta-carotene, though present in smaller quantities,
also have antioxidant properties and are required for good vision and retarding
age-related macular degeneration, healthy skin, and maintaining mucus
membranes. Pineapple is also a good source of thiamine. This component of
the vitamin B complex acts as a cofactor in enzymatic reactions central to
energy production and red blood cell formulation. Antioxidant-rich foods in
the diet can improve fertility. The bioavailability of nutrients is the proportion
of a nutrient that is absorbed from the diet and used for normal body functions.
Both external and internal factors govern the bioavailability of the nutrient.
External factors include the food matrix and the chemical form of the nutrient
in question, whereas gender, age, nutrient status, and life stage are among the
internal factors. Ascorbic acid and S-containing amino acids present in
pineapple are agents that promote micronutrient availability in the human
body, while polyphenolics and phytates are known to inhibit micronutrient
Bioavailability.

12



Chapter 2: BASIC THEORETICAL
2.1. General about drying technology.
2.1.1. Drying process.
Drying is the process of evaporating water out of a solid material by a heat
method.
The essence of drying is a diffusion process, consisting of diffusion of
moisture from the inner layer of the material to the outer surface layer and the
process of transferring moisture from the surface of the material to the
surrounding environment.
2.1.2. Drying methods classified
Normally, based on the drying agent state or how to create the dynamic of
the heat-moisture transition, it is divided into two drying methods, which are
the heating method and the cold-drying method.
1, Heating method.
In the heating method, to create a water vapor pressure difference between
drying agent and drying material, it is possible to heat to heat only drying agent
or drying material or both drying agent and drying material. Therefore, heating
systems are generally classified according to the heating method as follows:
a. Convection drying process.
Drying material receives convective heat from a hot liquid, usually air or
flue smoke. This is the most common type of drying system in the heating
method. In the convection drying system, it is classified into categories:
chamber drying system, tunnel drying system, rotary barrel drying system,
tower drying system, aerodynamic drying system,…
b. Contact drying system.
Drying material is in direct contact and receives heat from a hot surface.
Thus, in the exposed drying system, the pressure differential is created by
increasing the steam pressure differential from the contact surface with the

drying material.

13


c. Radiation drying system.
Drying material receives heat from a radiant wave source to allow
moisture to travel from within the drying material to the surface and from the
surface to diffuse into the medium. Apparently, in radiated drying system, the
water vapor pressure difference between the drying material and the medium is
created just by heating the object.
d. Microwave drying system.
The general principle of this technology is that when we place food in an
environment with microwaves (microwaves) with a high frequency of about
2450 MHz, these short waves are similar to radio waves going deep into the
food's heart, Carrying electricity - magnetic field, when meeting H2O water
molecules with polar structure from oxygen and hydrogen atoms, this structure
rotates and redirects in the direction of electric - magnetic field. Due to the very
large oscillation frequency of the microwave wave 2.45 billion times/s, the
electric field always changes polarity, making the water molecules always
fluctuate very quickly and generate heat due to friction. This generated heat
will be transferred to the inside of the object to heat the object and evaporate
the water. Based on the above principle in the past 15 years, people have
applied to manufacture large-scale microwave drying equipment for industrial
applications. Because the microwave has a short wavelength, the ability to
penetrate the object is only about 10cm, so this drying method is very suitable
for drying agricultural, food and medicinal products when the radius of drying
material is less than 10cm.
2, Cold-drying method.
Unlike the heating method, in the cold-drying method, a water vapor

pressure difference between drying material and drying agent is created by
reducing the pressure distribution in the drying agent by reducing the amount
of moisture. The cold drying method can be classified into two types drying
system:

14


a. Cold drying system at temperatures less than 0℃.
- Sublimation drying system: Sublimation drying is the process of
separating moisture from drying material directly from the solid state into a
vapor state base on the sublimation process. To induce sublimation, drying
material must be cooled below the triple point, ie the temperature of the
material t < 0°C and the pressure drying agent surrounding the object p < 610
Pa. From there, drying material receives the heat to allow moisture from the
solid state to sublimate into a gas and into the environment. Thus, in
sublimated drying system, a vacuum must be created around the drying
material and cooled down to below 0°C.
- Vacuum drying system: The vacuum drying method is a method to
create a nearly vacuum environment in the drying chamber, ie material
temperature t < 0°C, drying agent pressure surrounding the object p > 610 Pa.
When heat is received, the water particles in the drying material in a solid form
will turn into a liquid, then change to a vapor and enter the environment.
The vacuum drying method usually only dries drying materials that are
precious and easily degraded products. Due to the complexity and
uneconomical, sublimated drying system, vacuum drying system is only used
to dry rare drying material, which cannot withstand high temperatures.
Therefore, these drying system are specialized, uncommon drying system.
b. Cold drying system at temperatures greater than 0°C
- Method of using a dedicated dehumidifier combined with an air

conditioner:
This method uses a dehumidifier combined with an air conditioner, to create
a drying environment with a relatively low temperature, often equal to or less
than the ambient temperature from 5°C - 15°C.
- Drying method using low temperature pump:
In this method, only a heat pump system is used to create the drying medium.
The drying environment temperature can be adjusted within a fairly wide range
from approximate to negative temperatures, depending on the requirements of
15


the drying material. Unlike other refrigeration equipment, when using a heat
pump to dry and dehumidify, both the indoor and outdoor units are usefully
used, so the energy consumption here can be used to the highest extent. The air
temperature keeps normal be maintained at or below ambient temperature.
2.1.3. Drying agent.
The drying agent that loads the moisture has escaped the material out of the
drying chamber. Depending on the drying mode and the quality requirements
of the drying product, choose the appropriate type of drying agent. Common
drying agents are air, smoke, superheated steam and liquids.
2.1.4. Drying mode.
Drying mode is understood in the common sense as the process of
organizing the drying process, which is mainly the heat transfer and transfer
process between the drying agent and the drying material and the process
parameters to ensure productivity and quality, quantity and cost of drying.
In the reality of production, due to the nature of the drying material, the
requirement of drying technique and the economy of drying technology, many
different drying modes are conducted. Here are some common drying modes:
- The drying mode with intermediate heating.
- A part return drying mode of exhaust gas.

- Drying mode combines reflux and intermediate heating.
- Full return drying mode of exhaust gas.

2.2. General about Heat pump-drying.
In 1852, Thomson (Lord Kelvin) invented the world's first heat pump. Along
with cold technology, the heat pump has its own development. The greatest
success of heat pumps dates back to the 1940s when series of large-capacity
heat pumps were successfully installed in many European countries for
warming, heating water and air-conditioning.
16


Since the energy crisis in the early 1970s, the heat pump has entered a new
leap. Series of heat pumps of all sizes for different applications are researched,
manufactured, completed and widely sold in the market. Today heat pumps
have become very familiar in the fields of air conditioning, drying,
dehumidifying, water heating, ...
2.2.1. Principle diagram of Heat pump-drying
A heat pump is a device used to pump a stream of heat from a low
temperature to a higher temperature, to suit your heating needs. Another flow
of energy (electricity or heat) is consumed to keep the heat pump running. Thus,
an air conditioner is also a heat pump and has a common principle of operation.
Their devices are the same. People only distinguish the air conditioner from the
heat pump in terms of use only. Air-conditioning is associated with the use of a
cold source in an evaporator and a heat pump is associated with the use of a
heat source in the condenser.
Similar to air-conditioners, heat pumps work in reverse cycles, with the main
processes as follows:
1 - 2: the process of compressing the solvent vapor from low pressure, low
temperature to high pressure and high temperature in the compressor. The

compression process is adiabatic.
2 - 3: isothermal condensation in the condenser, discharging heat to the
environment.
3 - 4: throttling process isentropic entropy (h3 = h4) of the liquid through the
throttle valve from high pressure to low pressure.
4 - 1: the process of isothermal evaporation at low temperature and low
pressure, and heat recovery of a cold environment.

17


Picture 2.1 Equipment’s diagram
The main use of the heat pump is the heat discharged from the condenser.
Currently, people manufacture many types of heat pumps working on many
different principles such as heat absorption pump, pneumatic heat pump and
thermoelectric pump. In general, all of the above types of heat pumps are in use
today, but the pneumatic heat pump is the most widely used.
In addition, the four types of heat pumps mentioned above are also coupled
together to achieve certain efficiency. An example of an absorption heat
pump-compressing the vapor aims to increase the condenser temperature,
thereby increasing the heat load. The principle of operation is mainly like an
absorption air-conditioner, but between the steam generator and the condenser,
a compressor is installed to suck steam from the steam generator and compress
it into the condenser. The high condensing pressure brings up the high
condensing temperature, and its thermal coefficient increases significantly.

18


2.2.2. Coefficient of Heat pump-drying

To evaluate the efficiency of energy conversion, we use the heating
coefficient (heat pump coefficient) with the definition: Heating factor φ is the
amount of waste heat discharged to the hot source corresponding to a unit of
support work and is expressed as equals:
φ=

q k qo + l
= ε+1
=
l
l

If using a combined hot and cold heat pump, the economic efficiency is
much higher because it only takes one energy flow l to get both cold capacity
qo and heat capacity qk as desired.

Let φε be the heat coefficient of the heat pump, then:
φε =

qk + qo
= φ + ε = 2ε + 1
l

Thus, the heat coefficient of a heat pump is always greater than 1.
Therefore, the application of a heat pump is always thermally beneficial. The
heat coefficient of a heat pump plays an important role in improving the energy
efficiency of a heat pump.
The actual heat coefficient of the heat pump φz is less than the theoretical

heat coefficient calculated according to the Carnot cycle φc :

φz = v × φc

With two hot and cold sources with temperatures Tk and To , according to

the Carnot cycle we have:

Thus,

φc =

Tk
Tk . To

φz = v ×

Tk
Tk . To

Where v is the exergy efficiency or heat return coefficient of the real cycle.

19


Based on the above equation, we can see that the theoretical heat
coefficient can be calculated according to the Carnot cycle depending on the
temperature difference of the condenser and evaporator. In order for the heat
pump to achieve high economic efficiency, one must choose the temperature
difference ∆T so that the actual heat coefficient of the heat pump must reach

from 3 to 4 or more, that is, the temperature difference must be less than 60K.

It is also for that reason that only in special cases two levels of compression are
used. That is the important difference between heat pump and air conditioner.
2.2.3. Basic ingredients of Heat pump-drying
a. Refrigerant
Heat pump refrigerants and pairs have the same requirements as air
conditioners. Some of the more special requirements stem from higher boiling
and condensing temperatures, almost like the high temperature mode of air
conditioners, meaning that up to now people still use refrigerants like R22,
R502 and MR for turbine compressors. Recently, people have noticed the use
of new substances for heat pumps to raise the condenser temperature such as
R134, R113, R114, R142, etc.
b. Compressor
Similar to the refrigeration compressor, the compressor is the most
important part of the heat pump. All types of refrigeration compressors are
used in heat pumps. Of particular importance are the sliding piston compressors,
screw compressors and turbine compressors.
c. Heat exchangers
The basic heat exchangers in a heat pump are the evaporator and
condenser. Absorption coolers have additional steam generators and absorbers.
Like air conditioners, heat pump condensers and evaporators also come in the
following forms: beam tubes, tubes in tubes, vertical tubes and plate types. The
calculation methods are the same as the air conditioning mode.

20


d. Heat pump auxiliary equipment
All heat pump ancillary equipment is the same as that of an air
conditioner. Stemming from higher temperature requirements, higher reliability
and equipment processing technology are required. This is also a problem for

lubricating oils and seals of all kinds in the system.
e. Heat pump peripherals
Heat pump peripherals are the support devices for the heat pump that are
suitable for each of its uses. Heat pump peripherals include the following:
- The dynamic options of the compressor such as: electric motor, gas engine,
diesel engine or wind engine,...
- Plans for using heat collected in the condenser. If it is heating, the condenser
can be used directly or indirectly through a heat carrier circulation cycle, which
can be used for drying, cooking, dehumidification, etc. Each option requires
different supporting devices. .
- Heat supply options for the evaporator. The evaporator can be placed
outside, the evaporator uses well water as the heating medium. There are also
options such as an evaporator placed under water, placed on the ground or
using solar energy.
- Control devices, automatic testing of the operation of the heat pump and
supporting devices. These are devices that automatically control ancillary
equipment in addition to the heat pump to match the heat pump operation.

21


Chapter 3: CALCULATION AND DESIGN
3.1. Design plans
Due to the popularity as well as the design characteristics of the drying
system, we choose the drying agent as air, the exhaust gas return drying mode.
3.1.1. Initial figures
- Drying capacity of the device: G1 = 200kg/batch (Drying material input)
- Initial moisture of Pineapple: ω1 = 70%

- Required moisture of Pineapple after drying: ω2 = 8%

- Specific heat of Pineapple: Cm = 3,68 kJ/kgK
- Drying time: � = 8h

- Drying temperature: 45oC
- The installation location of the drying system is in Nghe An province.
3.1.2. Size of drying chamber
Based on the drying batch capacity and specific weight of pineapple, the
estimated number of trays needed to hold 200kg of pineapple is 30 trays. Can
dry 7kg/tray, equivalent to 200kg once drying. We have the size of the drying
chamber is 160 x 100 x 190 cm.

3.2. Theoretical and practical drying process.
3.2.1. Represent the theoretical drying process on the I-d graph.
a. I-d graph.

22


I, kJ/kgkk

�2

2

t2

3

t3
t1


4

�3
�= 1

1
d1 = d2

d3 = d4

d, kg/kgkk

Figure 3.1: I-d graph represents the theoretical drying process
1-2: The process of heating the drying agent to the drying temperature.
Point (2) is the state of hot air before entering the drying chamber.
2-3: Drying process. The low-moisture drying agent blown through the
drying material will receive the moisture released from the material and carry it
out of the drying chamber.
3-4: The process of cooling the drying agent to the dew point. Point (3) is
the state that the air after passing through the drying chamber is completely
recirculated, point (4) is the state of the air in the evaporator, at the beginning
of dehumidification.
4-1: Dehumidification process. Point (1) is the state of the air at the end
of the dehumidification stage.
b. Calculate the parameters at the points.
+ At point 0 : Outdoor parameters
Looking up documents [6], we have the average temperature and
humidity of Nghe An area as:
- Temperature: t0 = 10oC

- Humidity: φ0 = 86%
23