Evaporative cooling comfort in agricultural tractor cabin

Abstract

Evolution of automotive air conditioning was a remarkable milestone in the history of mankind. It has played an important role in human comfort and to some extent in human safety during vehicle driving in varied atmospheric conditions. This research focuses on providing comfort conditioning of a tractor cab which is a key factor in ensuring optimum working performance of the driver. A closed tractor cab acts like a greenhouse and its interior could become unbearable and sometimes even dangerous. Conventionally, vapor-compression refrigeration systems are standard for air conditioning in automobiles and account for up to 25 % of fuel consumption in the cooling season. Apart from conventional vapor-compression technology, this paper explores applicability of evaporative cooling in comfort conditioning of a tractor cabin which is an economical and eco-friendly alternative. The prototype performance lowered cabin temperature close to acceptable limit with less than 10 % of energy consumption compared to vapor-compression units when tested under similar hot-dry conditions.

Appendix 1

1. Air flow rate

$$ \begin{aligned} V_{\text{air}} = v \times A &= 2.5\;{\text{m/s}} \times 0.0706\;{\text{m}}^{2} \hfill \\ &= 0.175\;{{\text{m}^{3}/s}} \hfill \\ &= 175\;{\text{L/s}} \hfill \\ \end{aligned} $$

2. Air mass flow rate

$$ \begin{aligned} M_{\text{air}} = \rho V_{\text{air}} &= 1.08\;{\text{kg/m}}^{ 3} \times 0.175\;{\text{m}}^{ 3} / {\text{s}} \hfill \\ & = 0.189\;{\text{kg/s}} \hfill \\ \end{aligned} $$

3. The effectiveness of the cooling system can be estimated as follows (as per data in Fig. 5):

$$ \begin{aligned} \mu &= \left( {{\text{Ti}}_{\text{dbt}} - {\text{To}}^{\prime}_{\text{dbt}} } \right)/\left( {{\text{Ti}}_{\text{dbt}} - {\text{To}}^{\prime}_{\text{wbt}} } \right) \hfill \\ &= \left(43-29 \right)^{\circ}\rm {C}/\left(43-24 \right)^{\circ}\rm {C} \hfill \\ &= 73.6\;\% \hfill \\ \end{aligned} $$

4. Cooling load of the cabin (as per data in Fig. 5) [20]

$$ \begin{aligned} M_{\text{air}} \left( {h_{o\prime} - h_{o} } \right) &= 0.189\;{\text{kg/s}} \times \left( {82.13 - 72.41} \right)\;{\text{kJ/kg}} \hfill \\ & = 1.84\;{\text{kW}} \hfill \\ \end{aligned} $$

5. Water consumption (as per data in Fig. 5) [20]

$$ \begin{aligned} M_{\text{w}} &= M_{\text{air}} \left( {w_{i} - w_{o\prime} } \right) \hfill \\ &= 0.189 \text{kg/s} \times \left( {0.01693 - 0.0108} \right)\;{\text{kg/kg of dry air}} \hfill \\ &= 4.2\;{\text{kg/h}} \hfill \\ \end{aligned} $$