**3. Methodology: animals' thermal comfort**

Farm animals' thermal comfort is estimated for the viewpoint of optimum productivity. Different temperature and humidity values are required for different types of animals [7]. The heat transfer between farm animals and surrounding environment is expressed in **Figure 1a**. The heat transfer phenomenon between animal and environment is associated with conduction, convection, radiation, evaporation, evapotranspiration, wind velocity and metabolism rate (sensible and latent energy/heat transfer through animal skin). Heat transfer through building is also considerable while designing the animals' farm building. Temperature humidity index (THI) is one of the key parameters to measure the environmental condition for the farm animals. The thermal threshold values for Holstein Friesian cows are 72 for thermal neutral region and above than 72 for heat stress region [6]. The total heat load is calculated by following Eqs. (1)–(9). Total amount of heat is the sum of heat load for animals and heat load for building as shown in Eq. (8). Eq. (1) is used for the calculation of total heat load for animals [14] as follows:

$$\mathbf{Q\_a = q\_{skin} + q\_{res} + S} \tag{1}$$

(kPa), respectively. Total amount of heat transfer through buildings is calculated by

*Investigation of Desiccant and Evaporative Cooling Systems for Animal Air-Conditioning*

where, Qb is the total heat load for buildings (kW), U is overall heat transfer

where, Q is the total amount of heat load (kW). Temperature humidity index (THI) is important parameter which is used to measure the environment condition i.e., whether the region is in heat stress condition or in thermal neutral condition.

where, THI is the temperature humidity index [�], T is the temperature (°C), and RH is the relative humidity (%). As the THI is dependent on temperature and humidity, therefore, typical values of THI can also be found from the literature as given by reference [6]. A region is considered thermal neutral region when THI < 68, and the region is thermally stable region when THI = 68–72. The region is moderate heat stress region when THI = 72–80 and the region is severe heat stress region when THI > 80. Similarly, to cows and cattle, THI is also calculated for poultry birds [23, 27]. THI

where, T is the temperature (°C). The subscripts "db" and "wb" denote dry-bulb and wet-bulb, respectively. The interior dry-bulb and wet-bulb temperatures can be calculated according to the Eqs. (11) and (12). For the air-conditioned space by evaporative cooler, interior dry-bulb temperature and humidity ratio is calculated

ti*,* db <sup>¼</sup> to*,* db <sup>þ</sup> Qs age*,*to*,* db nbirdsmbirds � <sup>β</sup> <sup>m</sup>\_ <sup>w</sup> hfg

Wi <sup>¼</sup> Wo <sup>þ</sup> QL age*,*ti*,* db mbirds � <sup>β</sup> <sup>m</sup>\_ <sup>w</sup> hfg

subscripts "i," "o," "db," "wb," "S," "L," "a," and "w" denote inside, outside, dry-

There are many innovative modern AC technologies that are used globally in

addition to vapor compressor-based systems. These systems mainly use the

where, t is the temperature (°C), Q is the heat production (W), nbirds is the number of birds, and mbirds is the mass per bird (kg). The term β ṁ<sup>w</sup> represents the mass flow rate of the moisture in the air and hfg denotes latent heat of vaporization i.e., nearly 2.43 MJ kg�<sup>1</sup> at 30°C. The term Cp shows specific heat of air i.e., 1006 J kg�<sup>1</sup> K�<sup>1</sup>

m\_ acp

m\_ ahfg

equation for poultry applications is given by Eq. (10) as reported in Ref. [27]:

from sensible and latent heat equations for the building as follows:

bulb, wet-bulb, sensible, latent, air, and water, respectively.

**4. Proposed air-conditioning systems**

**27**

temperature difference (°C or K). Total amount of heat required for the thermal

comfort of farm animals is calculated by Eq. (8) as follows:

THI is calculated by the Eq. (9) [4, 6] as given below:

.K)], A is the area of building (m<sup>2</sup>

THI ¼ ð Þ� 1*:*8 T þ 32 ½ � ð Þ 0*:*55 � 0*:*0055 RH ð Þ 1*:*8 T � 26 (9)

Qb ¼ U A *ΔT* (7)

Q ¼ Qa þ Qb (8)

THI ¼ 0*:*6Tdb þ 0*:*4Twb (10)

), and ΔT is the

(11)

(12)

. The

Eq. (7) as given by:

coefficient for building [W/(m<sup>2</sup>

*DOI: http://dx.doi.org/10.5772/intechopen.88945*

where, Qa is total amount of heat for animals (kW), q is the partial heat load for the different sections (kW), and S is the amount of heat stored in the body (for ideal case: S = 0). The subscripts "a" and "res" denote animals and respiration, respectively. Heat load for respiration is calculated by the Eqs. (2) and (3) [14, 19] as given by:

$$\mathbf{q}\_{\text{skin}} = \mathbf{S}\_{\text{A}} \mathbf{M}\_{\text{R}} \tag{2}$$

$$\mathbf{S\_A} = \mathbf{0.147} \,\mathrm{W}^{0.57} \tag{3}$$

where, W is the weight of animal (kg), SA is the surface area of skin (m<sup>2</sup> ), and MR denotes the metabolism rate (met). The heat of respiration which is the sum of evaporation and convection heat loss is calculated by the Eqs. (4)–(6) [14].

$$\mathbf{q}\_{\rm res} = \mathbf{C}\_{\rm res} + \mathbf{E}\_{\rm res} \tag{4}$$

$$\mathbf{C\_{res}} = [0.0014 \,\mathrm{M\_R}(\mathbf{34} - \mathbf{T\_a})] \tag{5}$$

$$\mathbf{E\_{res}} = \begin{bmatrix} \mathbf{0}.\mathbf{0}\mathbf{1}7\mathbf{3} \ \mathbf{M}\_{\mathbb{R}}(\mathbf{5.87} - \mathbf{P\_{a}}) \end{bmatrix} \tag{6}$$

where, C is the convection heat loss from respiration [W/(h.m<sup>2</sup> )], E is the evaporation heat loss from respiration [W/(h.m<sup>2</sup> )], and MR is metabolic rate (met). The terms Ta and Pa represents ambient air temperature (°C) and vapor pressure

*Investigation of Desiccant and Evaporative Cooling Systems for Animal Air-Conditioning DOI: http://dx.doi.org/10.5772/intechopen.88945*

(kPa), respectively. Total amount of heat transfer through buildings is calculated by Eq. (7) as given by:

$$\mathbf{Q\_b} = \mathbf{U} \mathbf{A} \,\Delta T \,\tag{7}$$

where, Qb is the total heat load for buildings (kW), U is overall heat transfer coefficient for building [W/(m<sup>2</sup> .K)], A is the area of building (m<sup>2</sup> ), and ΔT is the temperature difference (°C or K). Total amount of heat required for the thermal comfort of farm animals is calculated by Eq. (8) as follows:

$$\mathbf{Q} = \mathbf{Q\_a} + \mathbf{Q\_b} \tag{8}$$

where, Q is the total amount of heat load (kW). Temperature humidity index (THI) is important parameter which is used to measure the environment condition i.e., whether the region is in heat stress condition or in thermal neutral condition. THI is calculated by the Eq. (9) [4, 6] as given below:

$$\text{LTH} = (\mathbf{1.8 T} + \mathbf{32}) - [(\mathbf{0.55} - \mathbf{0.0055 RH})(\mathbf{1.8 T} - \mathbf{26})] \tag{9}$$

where, THI is the temperature humidity index [�], T is the temperature (°C), and RH is the relative humidity (%). As the THI is dependent on temperature and humidity, therefore, typical values of THI can also be found from the literature as given by reference [6]. A region is considered thermal neutral region when THI < 68, and the region is thermally stable region when THI = 68–72. The region is moderate heat stress region when THI = 72–80 and the region is severe heat stress region when THI > 80.

Similarly, to cows and cattle, THI is also calculated for poultry birds [23, 27]. THI equation for poultry applications is given by Eq. (10) as reported in Ref. [27]:

$$\text{THI} = \mathbf{0.6T}\_{\text{db}} + \mathbf{0.4T}\_{\text{wb}} \tag{10}$$

where, T is the temperature (°C). The subscripts "db" and "wb" denote dry-bulb and wet-bulb, respectively. The interior dry-bulb and wet-bulb temperatures can be calculated according to the Eqs. (11) and (12). For the air-conditioned space by evaporative cooler, interior dry-bulb temperature and humidity ratio is calculated from sensible and latent heat equations for the building as follows:

$$\mathbf{t}\_{\mathbf{b},\mathbf{db}} = \mathbf{t}\_{\mathbf{o},\mathbf{db}} + \frac{\mathbf{Q}\_{\mathbf{s}} \left(\mathbf{a}\mathbf{g}, \mathbf{t}\_{\mathbf{o},\mathbf{db}}\right) \mathbf{n}\_{\text{birds}} \mathbf{m}\_{\text{birds}} - \boldsymbol{\beta} \text{ }\mathbf{n}\_{\mathbf{w}} \text{ }\mathbf{h}\_{\text{fg}}}{\mathbf{m}\_{\mathbf{a}} \mathbf{c}\_{\mathbf{p}}} \tag{11}$$

$$\mathbf{W}\_{\rm i} = \mathbf{W}\_{\rm o} + \frac{\mathbf{Q}\_{\rm L} \left(\mathbf{age}, \,\mathbf{t}\_{\rm b} \,\mathrm{db}\right) \mathbf{m}\_{\rm birds} - \beta \,\mathrm{in}\_{\rm w} \,\mathrm{h}\_{\rm fg}}{\mathrm{in}\_{\rm a} \mathbf{h}\_{\rm fg}} \tag{12}$$

where, t is the temperature (°C), Q is the heat production (W), nbirds is the number of birds, and mbirds is the mass per bird (kg). The term β ṁ<sup>w</sup> represents the mass flow rate of the moisture in the air and hfg denotes latent heat of vaporization i.e., nearly 2.43 MJ kg�<sup>1</sup> at 30°C. The term Cp shows specific heat of air i.e., 1006 J kg�<sup>1</sup> K�<sup>1</sup> . The subscripts "i," "o," "db," "wb," "S," "L," "a," and "w" denote inside, outside, drybulb, wet-bulb, sensible, latent, air, and water, respectively.

#### **4. Proposed air-conditioning systems**

There are many innovative modern AC technologies that are used globally in addition to vapor compressor-based systems. These systems mainly use the

**3. Methodology: animals' thermal comfort**

as given by:

**26**

**Figure 4.**

*Low-temperature Technologies*

Farm animals' thermal comfort is estimated for the viewpoint of optimum productivity. Different temperature and humidity values are required for different types of animals [7]. The heat transfer between farm animals and surrounding environment is expressed in **Figure 1a**. The heat transfer phenomenon between animal and environment is associated with conduction, convection, radiation, evaporation, evapotranspiration, wind velocity and metabolism rate (sensible and latent energy/heat transfer through animal skin). Heat transfer through building is also considerable while designing the animals' farm building. Temperature humidity index (THI) is one of the key parameters to measure the environmental condition for the farm animals. The thermal threshold values for Holstein Friesian cows are 72 for thermal neutral region and above than 72 for heat stress region [6]. The total heat load is calculated by following Eqs. (1)–(9). Total amount of heat is the sum of heat load for animals and heat load for building as shown in Eq. (8). Eq. (1)

*A view of: (a) cellulose evaporative pads [3]; and (b) schematic diagram of evaporative cooling system [7].*

is used for the calculation of total heat load for animals [14] as follows:

where, Qa is total amount of heat for animals (kW), q is the partial heat load for the different sections (kW), and S is the amount of heat stored in the body (for ideal case: S = 0). The subscripts "a" and "res" denote animals and respiration, respectively. Heat load for respiration is calculated by the Eqs. (2) and (3) [14, 19]

where, W is the weight of animal (kg), SA is the surface area of skin (m<sup>2</sup>

where, C is the convection heat loss from respiration [W/(h.m<sup>2</sup>

evaporation heat loss from respiration [W/(h.m<sup>2</sup>

MR denotes the metabolism rate (met). The heat of respiration which is the sum of evaporation and convection heat loss is calculated by the Eqs. (4)–(6) [14].

The terms Ta and Pa represents ambient air temperature (°C) and vapor pressure

Qa ¼ qskin þ qres þ S (1)

qskin ¼ SAM*<sup>R</sup>* (2) SA <sup>¼</sup> <sup>0</sup>*:*147 W<sup>0</sup>*:*<sup>57</sup> (3)

qres ¼ Cres þ Eres (4)

Cres ¼ ½ � 0*:*0014 M*R*ð Þ 34 � Ta (5) Eres ¼ ½ � 0*:*0173 M*R*ð Þ 5*:*87 � Pa (6)

), and

)], E is the

)], and MR is metabolic rate (met).

conception of evaporative cooling adsorption cooling and desiccant AC. These systems are not explored extensively in developing countries. Direct evaporative cooling system (swamp cooler) is most common system used worldwide wherever dry climatic conditions exists. Thermal comfort and/or temperature/humidity control are becoming more popular and demanding day by day in agriculture sector particularly for product storage, post-harvest processing, farm animals' buildings, as well as transportation of dairy, meat and food products [1, 15, 28, 29]. Thermal comfort for agricultural products and livestock requires cooling (temperature control) as well as humidity control and ventilation. These requirements change with the change in application and climatic conditions from one to another. Therefore, above mentioned thermally driven AC systems can be used for this purpose [5, 7, 8, 15].

#### **4.1 Standalone desiccant air-conditioning (D-AC) system**

Standalone desiccant air-conditioning (D-AC) system consists of a desiccant unit (wheel or block) mostly with the addition of heat-exchanger (HX). There is no cooling device principally used in the D-AC system. The D-AC system is used for the humidity control. It is relatively more efficient in the humid regions where humidity control is primarily required. It may also feasible for the applications in which humidity control is mainly concerned (i.e., storage of onion and leafy vegetables) [8, 11, 15, 26].

The schematic diagram of the D-AC system is shown in **Figure 5a**. The standalone D-AC system consists of two desiccant blocks (DB-1 and DB-2) used for the dehumidification of air. The dehumidified (relatively warmer) air is passed through the HX where the temperature of the air becomes equal to the ambient air (ideally). After that, the cooled air may be used for the desired application. The total process is known as the air dehumidification cycle. However, in regeneration cycle, the desiccant unit is regenerated by passing the hot air. Therefore, a heating unit is used D-AC system to heat up the air. Then the heated air is passed through the desiccant unit to remove its moisture in order to be used for cyclic process. The heating unit usually uses thermal energy sources i.e., waste heat, biogas, biomass, direct thermal energy (from solar or likewise), geothermal energy, etc. The regeneration depends upon the material type, ambient air conditions and other factors related to the material properties. Thus, regenerations temperature may be changed with the change in these factors.

A set of equations given by Jurinak model [9–13, 30] is used for performance evaluation of the desiccant unit.

$$\mathbf{F\_{1\\_ip}} = \frac{\mathbf{q\_1}}{\left(\mathbf{T\_{ip}} + 273.15\right)^{1.49}} + \tau\_1 \left(\frac{\mathbf{w\_{ip}}}{1000}\right)^{\gamma\_1} \tag{13}$$

$$\mathbf{F\_{2, ip}} = \frac{\left(\mathbf{T\_{ip}} + 2\mathbf{73.15}\right)^{1.49}}{\mathbf{q\_2}} - \tau\_2 \left(\frac{\mathbf{w\_{ip}}}{1000}\right)^{\mathbf{q\_2}}\tag{14}$$

$$\eta\_{\rm F1} = \frac{\mathbf{F\_{1,2}} - \mathbf{F\_{1,1}}}{\mathbf{F\_{1,8}} - \mathbf{F\_{1,1}}} \tag{15}$$

desiccant unit with the help of MS excel solver. The typical values for the efficiencies are taken as: (ηF1, ηF2) = (0.05, 0.95) for the high performance of desiccant unit

*Schematic diagram for: (a) standalone desiccant AC (D-AC) system and (b) M-cycle assisted desiccant AC*

*Investigation of Desiccant and Evaporative Cooling Systems for Animal Air-Conditioning*

*DOI: http://dx.doi.org/10.5772/intechopen.88945*

can be validated for the different climatic conditions (especially for developing countries). The processed air through the desiccant unit has higher temperature and low relative humidity as comparison with the ambient air conditions. The hot air passes through the heat exchanger where the temperature of the air decreases, but the humidity ratio remains constant. The temperature of the air is calculated by

The performance of the desiccant unit was evaluated by given equations and also

where, "ε" is the efficiency of the HX whose value is taken as 0.90. The T3 is the air temperature (°C) which has to be calculated. The T2 is the temperature (°C) of

*<sup>T</sup>*<sup>3</sup> <sup>¼</sup> *<sup>T</sup>*2*, db* � *<sup>ε</sup>HX <sup>T</sup>*2*, db* � *<sup>T</sup>*1*, db* (17)

as reported by [8–13]. The values for the constants are given in **Table 1**.

Eq. (17) [14].

**29**

**Figure 5.**

*(M-DAC) system.*

$$\eta\_{\rm F2} = \frac{\mathbf{F\_{2,2}} - \mathbf{F\_{2,1}}}{\mathbf{F\_{2,8}} - \mathbf{F\_{2,1}}} \tag{16}$$

where, F1 and F2 are combined potentials [�], and ηF1, ηF2 are the efficiencies of the combined potentials. The term "*ip*" indicates the state of air in the system (1, 2, and 8). Eqs. (13)–(16) are used for the performance evaluation of the

*Investigation of Desiccant and Evaporative Cooling Systems for Animal Air-Conditioning DOI: http://dx.doi.org/10.5772/intechopen.88945*

#### **Figure 5.**

conception of evaporative cooling adsorption cooling and desiccant AC. These systems are not explored extensively in developing countries. Direct evaporative cooling system (swamp cooler) is most common system used worldwide wherever dry climatic conditions exists. Thermal comfort and/or temperature/humidity control are becoming more popular and demanding day by day in agriculture sector particularly for product storage, post-harvest processing, farm animals' buildings, as well as transportation of dairy, meat and food products [1, 15, 28, 29]. Thermal comfort for agricultural products and livestock requires cooling (temperature control) as well as humidity control and ventilation. These requirements change with the change in application and climatic conditions from one to another. Therefore, above mentioned thermally driven AC systems can be used for this purpose

Standalone desiccant air-conditioning (D-AC) system consists of a desiccant unit (wheel or block) mostly with the addition of heat-exchanger (HX). There is no cooling device principally used in the D-AC system. The D-AC system is used for the humidity control. It is relatively more efficient in the humid regions where humidity control is primarily required. It may also feasible for the applications in which humidity control is mainly concerned (i.e., storage of onion and leafy

The schematic diagram of the D-AC system is shown in **Figure 5a**. The standalone D-AC system consists of two desiccant blocks (DB-1 and DB-2) used for the dehumidification of air. The dehumidified (relatively warmer) air is passed through the HX where the temperature of the air becomes equal to the ambient air (ideally). After that, the cooled air may be used for the desired application. The total process is known as the air dehumidification cycle. However, in regeneration cycle, the desiccant unit is regenerated by passing the hot air. Therefore, a heating unit is used D-AC system to heat up the air. Then the heated air is passed through the desiccant unit to remove its moisture in order to be used for cyclic process. The heating unit usually uses thermal energy sources i.e., waste heat, biogas, biomass, direct thermal energy (from solar or likewise), geothermal energy, etc. The regeneration depends upon the material type, ambient air conditions and other factors related to the material properties. Thus, regenerations temperature may be changed

A set of equations given by Jurinak model [9–13, 30] is used for performance

wip 1000 <sup>γ</sup><sup>1</sup>

wip 1000 <sup>γ</sup><sup>2</sup>

� τ<sup>2</sup>

(13)

(14)

(15)

(16)

Tip <sup>þ</sup> <sup>273</sup>*:*<sup>15</sup> <sup>1</sup>*:*<sup>49</sup> <sup>þ</sup> <sup>τ</sup><sup>1</sup>

<sup>η</sup>F1 <sup>¼</sup> F1*,* <sup>2</sup> � F1*,* <sup>1</sup> F1*,* <sup>8</sup> � F1*,* <sup>1</sup>

<sup>η</sup>F2 <sup>¼</sup> F2*,* <sup>2</sup> � F2*,* <sup>1</sup> F2*,* <sup>8</sup> � F2*,* <sup>1</sup>

where, F1 and F2 are combined potentials [�], and ηF1, ηF2 are the efficiencies of the combined potentials. The term "*ip*" indicates the state of air in the system (1, 2, and 8). Eqs. (13)–(16) are used for the performance evaluation of the

φ2

F1*,*ip <sup>¼</sup> <sup>φ</sup><sup>1</sup>

F2*,*ip <sup>¼</sup> Tip <sup>þ</sup> <sup>273</sup>*:*<sup>15</sup> <sup>1</sup>*:*<sup>49</sup>

**4.1 Standalone desiccant air-conditioning (D-AC) system**

[5, 7, 8, 15].

vegetables) [8, 11, 15, 26].

*Low-temperature Technologies*

with the change in these factors.

evaluation of the desiccant unit.

**28**

*Schematic diagram for: (a) standalone desiccant AC (D-AC) system and (b) M-cycle assisted desiccant AC (M-DAC) system.*

desiccant unit with the help of MS excel solver. The typical values for the efficiencies are taken as: (ηF1, ηF2) = (0.05, 0.95) for the high performance of desiccant unit as reported by [8–13]. The values for the constants are given in **Table 1**.

The performance of the desiccant unit was evaluated by given equations and also can be validated for the different climatic conditions (especially for developing countries). The processed air through the desiccant unit has higher temperature and low relative humidity as comparison with the ambient air conditions. The hot air passes through the heat exchanger where the temperature of the air decreases, but the humidity ratio remains constant. The temperature of the air is calculated by Eq. (17) [14].

$$T\_3 = T\_{2,db} - \varepsilon\_{HX} \left( T\_{2,db} - T\_{1,db} \right) \tag{17}$$

where, "ε" is the efficiency of the HX whose value is taken as 0.90. The T3 is the air temperature (°C) which has to be calculated. The T2 is the temperature (°C) of

### *Low-temperature Technologies*


lower than ambient air relative humidity due to adsorption of water by desiccant material. Feasibility of the standalone D-AC system for animal air-conditioning is checked by the THI analysis which clarifies the system's feasibility for desired application. **Figure 6b** shows the THI values of ambient and product air, as well as the permissible limit of heat stress. The permissible limit of heat stress for cows is 72. The THI of the ambient air as well as product air is higher than the permissible limit for the whole month. So, it may not be suitable for the ambient conditions of

*Investigation of Desiccant and Evaporative Cooling Systems for Animal Air-Conditioning*

The schematic diagram of Maisotsenko cycle (M-cycle) assisted desiccant air conditioning (M-DAC) system is shown in **Figure 5b**. It consists of desiccant unit with the addition of HX and an exclusive M-cycle unit. The M-cycle cooling device lowers down the temperature of the processed air from the HX. Therefore, this system can be used for the humidity and temperature control. This can be efficient in hot and humid climatic regions where temperature and humidity control are essential. It may also be efficiently feasible for the applications in which humidity and temperature control is concerned (i.e., agricultural storage and livestock applications) even in hot and humid climatic conditions [5, 11, 16, 26]. The system consists of two desiccant blocks (DB-1 and DB-2) used for the air dehumidification and regeneration purposes. The dehumidified air is passed through the heatexchanger where the temperature of the air becomes nearly equal to the ambient air. The air is further passed through the M-cycle unit where air is further cooled up to the desired temperature and humidity conditions to be used for desired application. The desiccant unit is regenerated by hot air and therefore a heating unit is principally required in this system which is supposed to be operated on low-cost thermal energy options. The heated air is passed through the desiccant unit to

It is important to mention that the M-cycle is an advanced indirect evaporative cooling conception that cools down the temperature of the working air up to the dew point by capturing energy from the air step by step as the humidity of the system remains constant [5, 16, 31, 32]. M-cycle is well-known in the air-

conditioning field due to its working range for the dew point evaporative cooling. The details can be found from authors' previous work as reported in [16]. Many researchers used different structures (channels) and materials for the manufacturing of the M-cycle channels as well as flow arrangements [8, 16, 31, 32]. In one-way configuration of M-cycle unit, the ambient air is passed through the dry channels (in cross flow direction to the wet channel) and then part of this air is mixed into the wet channel. The cyclic process brings the product air temperature to the dew point (theoretically) of the ambient air temperature. In another way configuration of M-cycle unit, the wet channel is sandwiched between two dry channels. Process air is passed firstly through one of the dry channels followed by the wet channel. In the cyclic process, this will lower the temperature of the product air passing through the other dry channel up to the ambient air wet bulb (finally approaches to the dew point) temperature. In authors' previous work [5], a simplified correlation was developed for performance evaluation of the M-cycle unit as given by following

> To <sup>¼</sup> A1 <sup>þ</sup> B1ð Þþ Ti C1 Hspc (18) <sup>Q</sup> <sup>¼</sup> A2 <sup>þ</sup> B2ð Þþ Ti C2 Hspc (19)

**4.2 M-cycle assisted desiccant air-conditioning (M-DAC) system**

remove moisture from the desiccant material for cyclic usage.

Multan for the month of July.

*DOI: http://dx.doi.org/10.5772/intechopen.88945*

Eqs. (18) and (19):

**31**

**Table 1.**

*Constants of Jurinak model for the evaluation of desiccant unit.*

#### **Figure 6.**

*Results of D-AC system for July (daily-basis) for climatic conditions of Multan, Pakistan: (a) temperaturehumidity profile and (b) THI profile.*

the dehumidified air after passing through the desiccant and the T1 is the ambient air temperature (°C).

**Figure 6** shows the results of the standalone D-AC system for July (daily based) according to climatic conditions of Multan, Pakistan. The data of temperature and humidity is the average data of 20 years obtained from the METRONOME software. The D-AC is evaluated in terms of system analysis and also THI analysis which elucidate the D-AC system's applicability for animal air-conditioning. **Figure 6a** shows the difference between ambient air temperature and relative humidity with the product air temperature and relative humidity. It is clear that the product air temperature is higher than ambient air temperature due to latent heat of adsorption [15, 29, 30]. However, relative humidity of product air from the D-AC system is

*Investigation of Desiccant and Evaporative Cooling Systems for Animal Air-Conditioning DOI: http://dx.doi.org/10.5772/intechopen.88945*

lower than ambient air relative humidity due to adsorption of water by desiccant material. Feasibility of the standalone D-AC system for animal air-conditioning is checked by the THI analysis which clarifies the system's feasibility for desired application. **Figure 6b** shows the THI values of ambient and product air, as well as the permissible limit of heat stress. The permissible limit of heat stress for cows is 72. The THI of the ambient air as well as product air is higher than the permissible limit for the whole month. So, it may not be suitable for the ambient conditions of Multan for the month of July.

#### **4.2 M-cycle assisted desiccant air-conditioning (M-DAC) system**

The schematic diagram of Maisotsenko cycle (M-cycle) assisted desiccant air conditioning (M-DAC) system is shown in **Figure 5b**. It consists of desiccant unit with the addition of HX and an exclusive M-cycle unit. The M-cycle cooling device lowers down the temperature of the processed air from the HX. Therefore, this system can be used for the humidity and temperature control. This can be efficient in hot and humid climatic regions where temperature and humidity control are essential. It may also be efficiently feasible for the applications in which humidity and temperature control is concerned (i.e., agricultural storage and livestock applications) even in hot and humid climatic conditions [5, 11, 16, 26]. The system consists of two desiccant blocks (DB-1 and DB-2) used for the air dehumidification and regeneration purposes. The dehumidified air is passed through the heatexchanger where the temperature of the air becomes nearly equal to the ambient air. The air is further passed through the M-cycle unit where air is further cooled up to the desired temperature and humidity conditions to be used for desired application. The desiccant unit is regenerated by hot air and therefore a heating unit is principally required in this system which is supposed to be operated on low-cost thermal energy options. The heated air is passed through the desiccant unit to remove moisture from the desiccant material for cyclic usage.

It is important to mention that the M-cycle is an advanced indirect evaporative cooling conception that cools down the temperature of the working air up to the dew point by capturing energy from the air step by step as the humidity of the system remains constant [5, 16, 31, 32]. M-cycle is well-known in the airconditioning field due to its working range for the dew point evaporative cooling. The details can be found from authors' previous work as reported in [16]. Many researchers used different structures (channels) and materials for the manufacturing of the M-cycle channels as well as flow arrangements [8, 16, 31, 32]. In one-way configuration of M-cycle unit, the ambient air is passed through the dry channels (in cross flow direction to the wet channel) and then part of this air is mixed into the wet channel. The cyclic process brings the product air temperature to the dew point (theoretically) of the ambient air temperature. In another way configuration of M-cycle unit, the wet channel is sandwiched between two dry channels. Process air is passed firstly through one of the dry channels followed by the wet channel. In the cyclic process, this will lower the temperature of the product air passing through the other dry channel up to the ambient air wet bulb (finally approaches to the dew point) temperature. In authors' previous work [5], a simplified correlation was developed for performance evaluation of the M-cycle unit as given by following Eqs. (18) and (19):

$$\mathbf{T\_o = A\_1 + B\_1(T\_i) + C\_1(H\_{\rm spc})} \tag{18}$$

$$\mathbf{Q} = \mathbf{A}\_2 + \mathbf{B}\_2(\mathbf{T}\_i) + \mathbf{C}\_2(\mathbf{H}\_{\mathrm{spc}}) \tag{19}$$

the dehumidified air after passing through the desiccant and the T1 is the ambient

*Results of D-AC system for July (daily-basis) for climatic conditions of Multan, Pakistan: (a) temperature-*

**Parameter Value Parameter Value** φ<sup>1</sup> [] 2865 φ<sup>2</sup> [] 6360 τ<sup>1</sup> [] 4.344 τ<sup>2</sup> [] 1.127 γ<sup>1</sup> [] 0.8624 γ<sup>2</sup> [] 0.07969

*Constants of Jurinak model for the evaluation of desiccant unit.*

**Figure 6** shows the results of the standalone D-AC system for July (daily based) according to climatic conditions of Multan, Pakistan. The data of temperature and humidity is the average data of 20 years obtained from the METRONOME software. The D-AC is evaluated in terms of system analysis and also THI analysis which elucidate the D-AC system's applicability for animal air-conditioning. **Figure 6a** shows the difference between ambient air temperature and relative humidity with the product air temperature and relative humidity. It is clear that the product air temperature is higher than ambient air temperature due to latent heat of adsorption [15, 29, 30]. However, relative humidity of product air from the D-AC system is

air temperature (°C).

*humidity profile and (b) THI profile.*

**Figure 6.**

**30**

**Table 1.**

*Low-temperature Technologies*

#### *Low-temperature Technologies*

where Ti and To represent the air temperature (°C) at inlet and outlet of M-cycle channels, respectively. The term Hspc represents the specific humidity (g/kg-DA) and Q represents the specific cooling capacity. The terms A, B, and C are the constants for simplified correlations, and optimized values for these constants are given in **Table 2**.

evaluated in terms of system analysis and THI analysis which elucidate the M-DAC system's applicability for animal air-conditioning. **Figure 7a** shows the difference between ambient air temperature and relative humidity with the product air temperature and relative humidity. It is clear from the figure that the product air temperature is lower than ambient air temperature due to water evaporation [30, 33–35]. However, relative humidity of product air is higher than ambient air

*Investigation of Desiccant and Evaporative Cooling Systems for Animal Air-Conditioning*

relative humidity which is required for animal air-conditioning.

*DOI: http://dx.doi.org/10.5772/intechopen.88945*

temperature).

**Figure 8.**

**33**

*region shows animal air conditioning zone.*

subjected to the conditions.

Thereby, feasibility of the M-cycle based D-AC system for animal airconditioning is checked by THI calculated from Eq. 9. **Figure 7b** shows the THI values of ambient air and product air, and permissible limit of heat stress is also shown in the figure. The permissible limit of heat stress for cows is 72. The figure clearly indicates that the THI of the ambient air is higher than the permissible limit for the whole month, while the THI of the product air is lower than permissible limit in most of the days. So, it may be feasible for the ambient conditions of Multan for the month of July (greater relative humidity and

The psychrometric representation of the product air of proposed AC systems according to the temperature and relative humidity values is shown in the **Figure 8**

with the help of different markers. The values are obtained for the ambient conditions of Multan, Pakistan for the month of July. The black color line box shows the thermal comfort zone for animals. The circular marker shows the ambient air conditions, triangular marker shows the D-AC system's air

conditions and diamond shaped marker shows M-DAC system's air conditions. The ambient conditions and D-AC output conditions are not able to provide the thermal comfort for animals. However, M-DAC output conditions are relatively suitable; therefore, this system can be applicable for animal air-conditioning

*Psychrometric plot of results identifying the feasibility of D-AC and M-DAC systems. Black line marked closed*

**Figure 7** shows the daily based analysis of M-cycle based D-AC system for the month of July for Multan, Pakistan. The data of temperature and humidity is the average data of 20 years obtained from the METRONOME software. The M-DAC is


#### **Table 2.**

*Numerical values of the constants of the simplified M-cycle correlations [5].*

**Figure 7.**

*Results of M-DAC system for July (daily-basis) for climatic conditions of Multan, Pakistan: (a) temperaturehumidity profile and (b) THI profile.*

#### *Investigation of Desiccant and Evaporative Cooling Systems for Animal Air-Conditioning DOI: http://dx.doi.org/10.5772/intechopen.88945*

evaluated in terms of system analysis and THI analysis which elucidate the M-DAC system's applicability for animal air-conditioning. **Figure 7a** shows the difference between ambient air temperature and relative humidity with the product air temperature and relative humidity. It is clear from the figure that the product air temperature is lower than ambient air temperature due to water evaporation [30, 33–35]. However, relative humidity of product air is higher than ambient air relative humidity which is required for animal air-conditioning.

Thereby, feasibility of the M-cycle based D-AC system for animal airconditioning is checked by THI calculated from Eq. 9. **Figure 7b** shows the THI values of ambient air and product air, and permissible limit of heat stress is also shown in the figure. The permissible limit of heat stress for cows is 72. The figure clearly indicates that the THI of the ambient air is higher than the permissible limit for the whole month, while the THI of the product air is lower than permissible limit in most of the days. So, it may be feasible for the ambient conditions of Multan for the month of July (greater relative humidity and temperature).

The psychrometric representation of the product air of proposed AC systems according to the temperature and relative humidity values is shown in the **Figure 8** with the help of different markers. The values are obtained for the ambient conditions of Multan, Pakistan for the month of July. The black color line box shows the thermal comfort zone for animals. The circular marker shows the ambient air conditions, triangular marker shows the D-AC system's air conditions and diamond shaped marker shows M-DAC system's air conditions. The ambient conditions and D-AC output conditions are not able to provide the thermal comfort for animals. However, M-DAC output conditions are relatively suitable; therefore, this system can be applicable for animal air-conditioning subjected to the conditions.

#### **Figure 8.**

where Ti and To represent the air temperature (°C) at inlet and outlet of M-cycle channels, respectively. The term Hspc represents the specific humidity (g/kg-DA) and Q represents the specific cooling capacity. The terms A, B, and C are the constants for simplified correlations, and optimized values for these constants are

**Figure 7** shows the daily based analysis of M-cycle based D-AC system for the month of July for Multan, Pakistan. The data of temperature and humidity is the average data of 20 years obtained from the METRONOME software. The M-DAC is

**Constant Value Constant Value Constant Value** *A*<sup>1</sup> [] 6.70 *B*<sup>1</sup> [] 0.2630 *C*<sup>1</sup> [] 0.5298 *A*<sup>2</sup> [] 5.48 *B*<sup>2</sup> [] 0.7317 *C*<sup>2</sup> [] 0.5946

*Results of M-DAC system for July (daily-basis) for climatic conditions of Multan, Pakistan: (a) temperature-*

*Numerical values of the constants of the simplified M-cycle correlations [5].*

given in **Table 2**.

*Low-temperature Technologies*

**Table 2.**

**Figure 7.**

**32**

*humidity profile and (b) THI profile.*

*Psychrometric plot of results identifying the feasibility of D-AC and M-DAC systems. Black line marked closed region shows animal air conditioning zone.*
